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Full text of "Chemistry no mystery; or, A lecturer's bequest. Being the subject-matter of a course of lectures, delivered by an old philosopher, and taken in short-hand by one of the audience, whose name is not known"

YALE 
MEDICAL LIBRARY 




HISTORICAL 
LIBRARY 

The Harvey Cmhing Fund 





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Saucing ©as. 



"Some jumped over the tables and chairs; some were 
bent upon making speeches ; some were very much inclined 
to fight ; and one young gentleman persisted in an attempt 
to kiss the ladies." 



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A LECTURER'S BEQUEST. 






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Page 1!>8. 

LONDON : 

HARVEY AND DARTON, GRACECHTTRCH STREET. 



CHEMISTRY NO MYSTERY; 

OR, 

A LECTURER'S BEQUEST. 

BEING THE SUBJECT-MATTER OF 

A COURSE OF LECTURES, 

Ucltberrti 65 an C5ID ^ijilosopjct, 

AND TAKEN IN SHORT-HAND BY ONE OP THE 
AUDIENCE, WHOSE NAME IS NOT KNOWN. 



"arranged from an ©rtginal Jlflanuscript, anB HUbfsetf, 



JOHN SC OFFER N, 

SURGEON; AND LATE ASSISTANT CHEMIST AT THE LONDON HOSPITAL, 
AND ALDERSGATE SCHOOL OF MEDICINE. 



LONDON : 
HARVEY AND DARTON, 

GRACECIIURCH-STREET. 



KEDICAt 



TO HER GRACE 

THE 

DUCHESS OF NORTHUMBERLAND, 

ARE RESPECTFULLY INSCRIBED, 
BY HER OBEDIENT SERVANT, 

JOHN SCOFFERN. 



CONTENTS. 



Preface . . . ix 

LECTURE I.— Page 1. 

Introduction— Meaning of the term Chemistry— Examples of 
Chemical Operations— Sketch of the History of Chemistry. 

LECTURE II.— Page 10. 

About the Imponderables, or Things which have no Weight. 

LECTURE III.— Page 25. 

Explanation of what is meant by the term Weight — Ponderable 
Bodies, or those which possess Weight — Specific Gravity. 

LECTURE IV— Page 32. 
Oxygen. 

LECTURE V.— Page 46. 

Nitrogen — Hydrogen. 

LECTURE VI Page 65. 

Chlorine. 



VI CONTENTS. 

LECTURE VII.— Page 75- 
Carbon. 

LECTURE VIII.— Page 85. 

Sulphur — Selenium — Phosphorus — Boron — Silicon. 

LECTURE IX.— Page 91. 

Compounds of the non-metallic simple Substances with each 
other— Oxygen and Nitrogen. 

LECTURE X.— Page 108. 

Protoxide of Nitrogen — Otherwise called Nitrous Oxide, or 
Laughing-Gas 

LECTURE XI.— Page 117. 

Binoxide of Nitrogen, or Nitric Oxide— Hyponitrous Acid 

Nitrous Acid— Nitric Acid. 

LECTURE XII.— Page 124. 

Compounds of Hydrogen and Oxygen — Water, Peroxide of 
Hydrogen. 

LECTURE XIII.— Page 142. 

Compounds of Oxygen with Chlorine — Iodine Bromine — 

Carbon, Carbonic Oxide, Carbonic Acid. 

LECTURE XIV._Page 158. 
Compounds of Oxygen with Sulphur. Hypo-sulphurous Acid ; 
Sulphurous Acid; Hypo-sulphuric Acid; Sulphuric Acid. 
Compounds of Oxygen with Selenium— Phosphorus— Boron 
and Silicon. 



CONTENTS. \ii 

LECTURE XV.— Page 164. 

Compound of Nitrogen with Hydrogen — (Ammonia) — with 
Chlorine — Iodine — Carbon. 

LECTURE XVI Page 171. 

Compounds of Hydrogen with Chlorine — Iodine — Bromine — 
Fluorine — Carbon — Sulphur — Selenium — Phosphorus. 

LECTURE XVII.- Page 200. 
Metals. 

LECTURE XVIII— Page 232. 

Substances which are formed by the union of Compounds with 
each other. 

LECTURE XIX.— Page 250. 

Analytical Chemistry — Toxicology, or the Chemistry of Poisons. 

LECTURE XX Page 264. 

Remarks on Gravitation, Cohesion, and Affinity— Single and 
double Elective Affinity — Single and Double Decomposition. 

LECTURE XXI.— Page 271. 

Introduction to Organic Chemistry— Differences existing between 
the structure of Organized and Inorganized Bodies — Dif- 
ference between Animals and Vegetables — Proximate Vegeta- 
ble Principles. 



CORRIGENDA. 

Page 6, line 22, far fifty-five read fifty-four. 

— 51 — a — ditto — ditto. 

— 62 — 26 — one — five. 



PREFACE. 



T7ie unknown author of these manuscripts re- 
lates the circumstances connected with the 
first origin of a literary and scientific insti- 
tution, somewhere in Devonshire, after the 
manner of that at Arcueil, in France. 



In the most lovely part of the southern coast 
of Devonshire is my native village ; which, on 
account of the purity of its air, and the beauty 
of its surrounding scenery, has long been known 
as a favourite resort for invalids. Visitors we had 
many, but strangers none; hospitality having 
long banished the word from our vocabulary : 
or if some had considered themselves in that 
light on their first arrival, a few days' residence 



X PREFACE. 

amongst us soon induced them to alter their 
minds, and made them feel quite at home. 
This state of society naturally brought with it 
many pleasures, but also much that was sad ; 
for the circumstances that enabled us to find 
new friends also contributed to make us lose 
them ; and many were our regrets for the de- 
parture of those whom, probably, we should 
see no more. 

But of all our visitors one holds a pre-eminent 
seat in nry memory, as having conferred on us 
a great and lasting benefit. He was an infirm 
and care-worn old man, whose mind, however, 
enjoyed its primary vigour, while his body was 
fast sinking under the weight of disease, and 
old age. What had been his avocations 1 know 
not, but he was thoroughly acquainted with 
scientific information, and delighted in impart- 
ing it to those around him, and on this account 
we gave him the name of the Old Philosopher. 

It was during a walk which he took with us 
one morning along the beach, that his conver- 
sation turned on the re-establishment of peace ; 



PREFACE. xi 

for I should remark, the French revolutionary 
wars had just ceased. He proceeded to inform 
us that the French literary and scientific men 
had established, at a village named Arcueil, a 
philosophic institution, from which great bene- 
fits would most probably accrue to every de- 
partment of learning. " One can hardly ima- 
gine," said he, " that so many highly talented 
men will concentrate their energies into one 
focus without producing some great and im- 
portant results. For my own part, I am very 
sanguine that their scheme will meet with all 
the success it deserves, and I think their exam- 
ple should be very generally followed. Indeed 
I should much like to establish such an institu- 
tion in this very place, and if my friends will 
support me in the undertaking it shall forthwith 
be done." 

The old gentleman now ceasing for an in- 
stant, gave a penetrating glance at our features, 
to see if we accorded with his proposal ; and, 
without waiting for an answer, because he said 
by the expression of our faces that we were 



xii PREFACE. 

delighted at the idea, he immediately replied, 
" Then let us commence to-morrow ; I engage 
to furnish you with a room, and to deliver the 
first course of Lectures, which shall be on Che- 
mistry." — On the morrow we met, each of us 
prepared with a note-boot, for the purpose of 
taking extracts ; and one of our party, who 
wrote short-hand, actually managed to copy 
almost verbatim the greater part of our Lec- 
turer's discourse. 

Such, then, was the origin of our little Philo- 
sophic Institution, which for many years flou- 
rished well. Season after season its founder 
returned and added to our fund of information ; 
but death at length removed our benevolent 
old friend from the scene of his earthly la- 
bours ; time and circumstances drove us from 
our early homes to mix in the busy scenes of 
active life ; each passing year witnessed the 
gradual decline of our little society, and now 
it exists no more. 



PREFACE. xiii 

Such is the commencement of an original 
manuscript, which, together with the extracts 
alluded to, are now in the editor's possession, 
and from which the following Lectures have 
been arranged. How he obtained the precious 
documents it is scarcely necessary to tell; — 
should his young friends think it worth their 
while, they may exercise their ingenuity by an 
investigation of the subject. 

Although the editor does not consider it ne- 
cessary to state by what means the materials of 
the following Lectures were obtained; he begs 
leave to remark, that he, himself, is interested 
in their success, and will be delighted if they 
render the science of chemistry at all more 
accessible to youthful minds. 

Should the following Lectures meet with 
approbation, there are more of them on other 
subjects, which at some future period may be 
arranged for the youthful public, by 

Their ever obedient Servant, 

John Scoffern. 



CHEMISTRY NO MYSTERY. 



LECTURES ON CHEMISTRY. 



LECTURE I. 

INTRODUCTION MEANING OF THE TERM CHE- 
MISTRY EXAMPLES OF CHEMICAL OPERA- 
RATIONS SKETCH OF THE HISTORY OF CHE- 
MISTRY. 

My dear young Friends, 

If I were to present myself before you 
with an offer to teach you some new game : — if 
I were to tell you an improved plan of throw- 
ing a ball, of flying a kite, or of playing at leap- 
frog, oh, with what attention you would listen 
to me. Well, I am going to teach you many 
new games. I intend to instruct you in a sci- 
ence full of interest, wonder, and beauty; a 
science that will afford you amusement in your 
youth, and riches in your more mature years. 

B 



2 INTRODUCTION. 

In short, I am going to teach you the science 
of chemistry. 

Chemistry ! I think I hear you repeat with 
a sneer — chemistry ! Then we must make our 
faces and hands black with charcoal, burn our 
clothes into holes with oil of vitriol, and work 
ourselves into a fever with the exertion of blow- 
ing a great pair of bellows. No such thing. I 
grant, that in former times it was thought ne- 
cessary to the successful study of chemistry, 
that one should have a large collection of in- 
struments, such as furnaces, stills, and cruci- 
bles ; besides an immense number of others, 
whose uncouth names almost make a person 
laugh ; but such is not necessary now ; and in- 
deed I may mention, that one of the greatest 
chemists of the present century, I mean Dr. 
Wollaston, had so few instruments, and those so 
very small, that he kept them all in a common 
tea-tray. As for furnaces, they are only neces- 
sary to persons who study chemistry more as a 
matter of profit than of science. A melter of 
brass would employ a furnace, because he ope- 
rates on large quantities ; but I shall teach you 
how to melt brass with the flame of a common 
candle. This, however incredulous you may 
be of what I tell you, is really very easy to be 



INTRODUCTION. 3 

done. I hope, then, I have convinced you 
that a person may study chemistry without 
soiling his face or hands, without burning him- 
self, and without great bellows and furnaces. 
But still you may imagine that its comprehen- 
sion may be too difficult. You do not under- 
stand the meaning of the term chemistry, and 
you think that young people cannot possibly en- 
gage themselves in the study of a science which 
has been cultivated by such great men as Sir 
Humphry Davy and Doctor Wollaston ; — this 
supposition is wrong. I grant that the very 
highest order of intellect is often required to 
make a discovery ; but when once made it may 
perhaps be rendered comprehensible to persons 
much younger than yourselves ; and indeed I 
cannot think of any necessary portion of che- 
mical science, which does not admit of a very 
easy and agreeable exemplification. 

Before commencing the study of any science, 
it is usual, in systematic books, to explain the 
meaning of terms ; and I might explain or de- 
fine to you the meaning of the term chemistry ; 
but as I do not like mere definitions without 
instances, let me give you a few cases of che- 
mical operations. I fear you will laugh at 
their simplicity, but never mind that. To 

B 2 



4 EXAMPLES OF CHEMICAL OPEKATIONS. 

begin then. Suppose you had some wet sand, 
and w ished to dry it, how would you proceed ? 
My question amuses you I dare say, but I have 
very little doubt that you cannot give me the 
reason of all you do, even in the simple ope- 
ration of drying sand. I know very well how 
you would proceed. You would put a plate 
over the fire, and on this plate you would place 
the sand; presently steam would arise, and the 
sand would become dry; but just at this period 
crack would go the plate. Now, my young 
philosophers, you laughed at my asking you so 
simple a question as how to dry sand, and I 
will avenge myself by demanding the why and 
the wherefore of all that has occurred. Why 
did the process of heating the sand cause the 
water to fly off in steam ? Why did the plate 
break ? Ah ! you cannot answer me. Now 
in drying sand, you have performed a chemical 
operation, and if you knew chemistry you would 
be enabled to offer an explanation of all that 
has occurred. We will have two or three in- 
stances more, if you please. 

Some time since a lady fancied that her moist- 
sugar contained an impurity : what it was she 
could not tell, but she knew by its taste that 
some improper substance was mixed with it. 



EXAMPLES OF CHEMICAL OPERATIONS. 5 

In order to satisfy herself on this point she sent 
some for examination to a gentleman who un- 
derstood chemistry, and this gentleman proved 
most satisfactorily that the sugar was mixed 
with salt. Now I will tell you how he pro- 
ceeded to discover this. Sugar is capable of 
being dissolved in spirits-of-wine, but salt is 
not ; he therefore boiled the lady's sugar with 
spirits of wine, and having done this, he found 
that something remained behind, which the 
spirits of wine would not dissolve. This some- 
thing he proved to be salt. 

I will give you another instance of a che- 
mical operation, in which indeed I was person- 
ally concerned. About two months ago I was 
near witnessing the death of a much-valued 
friend, by poisoning, from a preparation of 
copper. He had just eaten some pickles, when 
suddenly he became so very sick and ill, that I 
at once suspected he had been poisoned. On 
looking at the pickles, (which appeared very 
green,) my suspicions were strengthened, and I 
immediately settled all doubts, by pouring on 
some of the suspected pickle a little hartshorn, 
when immediately there was produced a beau- 
tiful blue colour. Now T knew that nothing but 
copper could have done this, and I therefore 
immediately attended to my friend, to whom I 



HISTOKY OF CHEMISTRY. 



administered some white of egg, beaten up with 
water, and by this treatment I probably saved 
his life. Here then you have two instances of 
chemical ojjerations — that of hartshorn striking 
a blue colour with the preparation of copper, 
and that of the white of egg in destroying its 
poisonous action. By this time I think you 
must have some idea of the nature and value of 
chemical knowledge. 

I dare say you would like to know something 
about the history of chemistry, and in order to 
gratify your curiosity, I will give you a short 
account of its commencement and progress. 
The ancient Greeks and Romans knew very 
little of chemistry, as indeed I shall soon con- 
vince you. Every one has heard of the four 
elements,— fire, air, earth, and water; those 
were the four elements of the ancients, and 
of which they believed that every thing 
was composed. Now modem chemists have 
shown, that instead of four elements there 
are in reality fifty-five, consequently you may 
imagine how very little the ancient Greeks and 
Romans knew about the science. 

Chemistry first originated in Arabia, and the 
celebrated Haroun Alraschid, whom you have 
so frequently read of in the Arabian Tales, 
himself admired and cultivated it. Geber and 



HISTORY OF CHEMISTRY. 7 

Avicenna were two great Arabian chemists, 
whose works remain to the present day. 

The Arabians were a very warlike race, and 
having subdued all the nations on the northern 
coasts of Africa, they crossed over into Spain, 
A. D. 712, the greater part of which nation they 
conquered, after a severe struggle, and from 
which they were not expelled until the year 1492. 
The Arabians carried with them, into Spain, 
their fondness for scientific learning, and from 
this nation was chemistry diffused over Europe. 
After the learning of the Arabians had spread 
beyond the boundaries of Spain, there arose a 
celebrated class of men called alchemists. Most 
persons have heard of the alchemists, and I 
here present you with the picture of one. 




8 ALCHEMY. 

An old man sitting amongst a heap of bot- 
tles, stills, fire-shovels, and other instruments, 
apparently engaged in deep thought, and most 
likely bent on the preparation of some mystic 
compound. 

I need not tell you what the object of the 
alchemist was to accomplish, for you are well 
aware that his business, if I may so term it, was 
to make gold, and to prepare a medicine 
which should render man immortal. Roger 
Bacon, who lived in the thirteenth century, 
affirmed that an alchemist, named Artephius, 
died in his time, at the very advanced age of 
one thousand and twenty -Jive years ! having 
prolonged his life to this good old age by the 
miraculous power of his medicines. If this be 
true, Artephius must have seen the world in a 
very early state, and the antiquity of alchemy 
must indeed be great; but unfortunately for the 
credit of this worthy old man, history has been 
pleased to fix the date at which the first 
European alchemist ever lived, as late as the 
eleventh century, and even the commencement 
of the art no earlier than the fifth. 

One of the alchemists, named Paracelsus, 
was impudent enough to say that he could live 
as long as he liked; but in spite of this boast 



ALCHEMY. 9 

he died at the comparatively early age of forty- 
two. 

1 need not tell you that the alchemists never 
succeeded in their endeavours to make gold, 
and to prevent people from dying; on the con- 
trary, they were generally poor themselves, 
and for the most part died at untimely periods 
of life. After the dark ages had ceased, and 
people began to make more use of their reason- 
ing facidties, the alchemists got well laughed 
at, as indeed they deserved to be; consequently, 
instead of trying to make gold, and to prepare 
a medicine which should render people immor- 
tal, those who studied the science began to 
apply their knowledge to real advantage; and 
now the term alchemy was changed to che- 
mistry. This, my young friends, is a very 
slight sketch of the history of chemistry, and in 
our next Lecture we will, if you please, enter 
upon the scientific part of our undertaking. 



10 



LECTURE II. 

ABOUT THE IMPONDERABLES, OR THINGS 
WHICH HAVE NO WEIGHT. 

Perhaps my hearers will startle a little, when 
I tell them I am going to describe the nature of 
the imponderable agents. Imponderable ! — what 
a long word ! Well, I grant that imponderable 
is a long word, but nevertheless a very easy 
word to understand ; it merely means some- 
thing which has no weight. If I were to give 
you a pair of scales and weights, and tell you 
to weigh a spoon, a fork, or a poker, you could 
do so easily enough ; but how you would laugh 
if I were to tell you to weigh a sun-beam, or 
the light of a candle, or the heat which is 
given out by the fire. It would be a ridiculous 
request for me to make indeed, and I merely 
suppose myself doing so, just to fix a fact in 
your memory. Light and heat cannot be 
weighed, neither can another substance, termed 
electricity. — Consequently 



imponderable agents. 11 

Light, 

Heat, 

Electricity 
are imponderables. 

Now the sources of light are various, but the 
greatest of all is the sun. Light takes about 
eight minutes to pass from the sun to the earth, 
a distance of nearly ninety-five millions of 
miles, travelling therefore with the immense 
velocity of two hundred thousand miles in a 
second of time ! Whereas a cannon-ball, when 
it first leaves the mouth of the gun, takes three 
seconds to travel one mile ; and if it could con- 
tinue its course with undiminished rapidity, it 
would occupy ten years in reaching the sun ! 
These facts will awaken in your mind feelings 
of wonder and admiration for that Great Being 
who had the power to create a substance so 
mysterious. You may, perhaps, think me 
wrong in calling light a substance, but one is 
obliged to do so for want of a better term. 

Although we are aware of the rapidity with 
which light travels, and although we know that 
it is the cause of vision, yet there is a difficulty 
experienced in determining the actual nature of 
light. Sir Isaac Newton believed that it con- 
sisted of small particles continually darted 



12 THEORIES OF LIGHT. 

away from luminous bodies, and which, by fall- 
ing on the delicate nerve of the eye, with a cer- 
tain force, produced vision. This philosopher 
imagined that the particles of which I speak were 
not all of the same size ; those producing red 
light being largest, and those producing violet 
light smallest. But this theory has, in great mea- 
sure, given way to another, according to which it 
isimagined that light consists of waves, produced 
in a medium called ether ; which ether is not 
only rjresent between the sun and the earth, 
but exists in every part of creation. 

When a stone is thrown into water, you know 
waves are produced, which keep spreading 
further and further from the spot where the 
stone was thrown, until all the water in the 
pond becomes agitated: well, just as those 
waves are propagated in water, so is it imagined 
that others are in ether; and it is presumed that 
the violet light is produced by small waves, and 
the red light by large ones. It is impossible 
for me to tell you which of those two theories 
is correct ; the question cannot be answered by 
much abler men than I am ; but for my own 
part I greatly prefer the theory of waves. 

Heat is said, by chemists, to be caused by a 
substance termed caloric ; but what this caloric 



HEAT EFFECTS OF. 13 

may be no one knows. A late opinion is, that 
when there occur in the ether, which I have 
just mentioned, waves larger than are necessary 
to produce red light, then those very large 
waves give rise to heat ; this point, however, 
must be settled by more clever men than our- 
selves. We, if you please, will have a few 
words about the properties of heat, leaving out 
of the question that which produces it. 

Now in order to learn a little about heat, let 
me suppose that you put a poker in the fire, 
and keep it there until it becomes red-hot. Just 
consider what you learn, even by this simple 
experiment. You learn that heat will pass 
from one body to another ; because it has 
passed from the materials in the fire-place to 
the poker : this is called transference ; you also 
learn that heat is capable of traversing, or of 
being conducted from one end of the poker to 
the other, this is termed conduction : you more- 
over learn that a great quantity of heat makes 
bodies luminous, inasmuch as the poker be- 
comes red, and gives out light ; chemists term 
this luminousness " incandescence.''' If you 
were to measure the poker when cold, and after- 
wards when hot, you would find that by heating, 
it increases very much in size, or, in scientific 



14 EXPANSION CAUSED BY HEAT. 

language, becomes expanded. If in place of a 
poker you were to employ a piece of stick, 
then instead of mere incandescence you would 
have an instance of combustion. It appears, 
then, that amongst the leading properties of 
heat, are a capability of being transferred and 
conducted, also of producing expansion, incan- 
descence, and combustion. 

Now I may explain to you the reason why 
the plate was supposed to break in the imagi- 
nary experiment of drying wet sand. You 
have just been informed that heat expands 
bodies, that is to say, makes them larger ; now 
the outside of the plate, or that part in con- 
tact with the fire, was necessarily hotter than 
the inside, on which was placed the sand ; con- 
sequently it was larger, or rather strived to be- 
come larger, and in doing so tore itself away 
by main force from the inner and cooler part : 
hence arose the crack. Whenever, then, you 
have occasion to heat brittle bodies do so gra- 
dually, in order that one part may not be very 
hot at the same time that another part is very 
cool, by this means you will be likely to pre- 
vent a fracture. 

A pretty instance of the expansion of bodies 
by heat is seen in the inflation of a fire-balloon, 



DEGREE OF HEAT, HOW ASCERTAINED. 15 

which is a large oval bag of tissue-paper, hav- 
ing a wide neck, kept extended by means of a 
wire. In this neck is placed a piece of sponge 
soaked in spirit-of-wine. Now this balloon 
is caused to ascend by proceeding as follows : 
let two or three persons separate its sides, while 
another applies a light to the sponge. The 
spirit-of-wine when burning produces a large 
flame, which makes the air inside the balloon 
very hot, therefore this air expands or increases 
in size, and the balloon being incajjable of 
holding the whole, a portion of it escapes, 
consequently the balloon is filled with air of 
extreme lightness, and therefore ascends. 

A more useful application of the expansion 
of bodies by heat, is seen in the construction 
of the thermometer, which is an instrument 
for ascertaining how hot, or how cold any sub- 
stance may be. Perhaps, you think that the 
quantity of heat or of cold may be ascertained 
by the sense of touch ; but in this idea you are 
quite mistaken, as I shall presently demon- 
strate. I will suppose that you are placed with 
naked feet in a room which is but partially 
carpetted, and without a fire. Whilst standing on 
the carpet, your feet do not feel very cold ; you 
step from the carpet upon the wooden floor, 



' 



16 SENSATIONS OF HEAT FALLACIOUS. 

and feel much colder ; you then place your feet 
upon the marble hearth and exclaim, bless me, 
how very cold ! one step more brings your feet 
in contact with the fire-irons, when your very 
teeth chatter because the sensation of cold is 
intolerable. 

Now, if you were asked which was coldest, 
the carpet, the wood, the marble, or the fire- 
irons, you would think the question a very silly 
one, and without consideration you would im- 
mediately answer, oh ! the fire-irons, to be sure. 
How much then will you be surprised when I 
affirm that they are all of the same tempera- 
ture, and that your feelings have been in a 
manner telling untruths. If we light a fire in 
the grate, then what will be the consequence ? 
why the carpet will feel cool, the wood warmer, 
the marble hearth hot, and the fire-irons,— O, 
touch them not! they would burn you. Perhaps 
you are aware, that the higher we ascend in 
the air the greater cold do we experience ; 
hence it is that on the tops of high mountains 
there exists perpetual snow. Having remarked 
thus much, I will relate to you a tale. Once 
upon a time, as reports say, two travellers were 
engaged in exploring the celebrated Mont 
Blanc. One traveller having got half-way up 



MODIFYING CIRCUMSTANCES. 17 

met the other traveller, who had got half-way 
down : " Bless me, how cold !" said the ascending 
traveller: "Bless me, how hot!" saidthe descend- 
ing one. Do you not understand the reason of 
these remarks ? The ascending traveller kept 
losing heat, the descending one kept gaining 
heat, and this solves the whole mystery. 

1 ou see, then, that our feelings are not cor- 
rect in their estimation of heat and cold : not 
only you but the poor travellers were mistaken ; 
thei'efore, to prevent future mistakes, let us in- 
vestigate the subject a little more narrowly. 

We find that the sensations of heat and cold 
do not depend upon the actual quantity of heat 
possessed by any substance, but upon the dif- 
ference existing between its temperature and 
the temperature of the hand or other part of 
the body which touches it ; also upon the faci- 
lity with which substances conduct or carry 
away heat. Now a woollen cloth, being a very 
bad conductor of heat, could not take away the 
heat of the feet, hence it seemed warm; and 
the fire-irons (like all metallic bodies) con- 
ducted or carried away the heat very fast, and 
hence they appeared cold. Just as woollen 
cloth will not carry away heat from you, neither 

c 






18 THERMOMETER. 

will it convey heat to you ; therefore it was 
that the celebrated Fire King always wrapped 
himself in flannel when he entered the hot 
oven. Unscientific people thought he did so to 
make himself hotter, but he very well knew 
that the flannel kept him very much cooler 
than he otherwise would have been. 

Remember, then, that there exists nothing in 
the nature of flannel to render it hotter than 
wood, or stone, or iron ; only it is a bad con- 
ductor of heat, and hence in common language 
is termed warm. 

Well, then, if one is not to believe his own 
feelings, what is he to believe ? Why there is a 
little instrument called a thermometer, which 
very prettily gives us all the information we re- 
quire respecting the temperature of bodies. 
You remember my telling you that hot sub- 
stances were larger than cold ones ; on this 
very principle is constructed the thermometer. 
Thermometer tubes are filled with various 
substances, but 1 shall describe the mercurial 
thermometer. First, then, let me inform you 
that there exists a metal which, unlike every 
other, is a liquid at ordinary temperatures : — 
tins metal I allude to is named quicksilver or 
mercury. 






THERMOMETER. 



19 




This plate represents a mercurial 
thermometer. You see it consists 
of a glass tube having a very small 
bore ; one end of the tube has been 
blown into a bulb, which is full of 
mercury, and the other end is closed. 
Those marks which you observe 
with figures attached to them are 
called degrees. Now, on touching 
this bulb with my warm hand, the 
mercury rises in the tube, because 
the heat makes it so large that the 
mere bulb cannot contain it. The hotter 
the quicksilver is made, the larger does it 
become, and consequently the higher does it 
rise. The heat of my hand has caused the 
quicksilver to rise as far as ninety degrees ; 
therefore I know that the temperature of my 
hand is equal to ninety degrees. Instead of 
mercury, some thermometers contain spirits of 
wine ; but whatever the fluid may be, the prin- 
ciple of its action is the same. Now, about 
electricity, or the electric fluid, I shall say but 
little. Perhaps you have heard of the electrical 
machine, and I may tell you, that by means of 
this machine we are enabled to collect or force 
into a small space a great quantity of a very 

c 2 



20 ELECTRICITY. 

peculiar imponderable substance, termed elec- 
tricity. Electrical machines are merely neces- 
sary when it is required to operate with great 
quantities of electricity, or the electric fluid ; 
and I can give you some idea of the properties 
of this electricity without the employment of 
any machine at all. 

First, tie a very light feather to the end of a 
piece of silk, and then suspend it from any con- 
venient support. Now take a piece of sealing- 
wax, which briskly rub upon flannel, and then 
bring it into contact with the feather; the latter 
will appear to be endowed with life, and will 
approach the sealing-wax until both come into 
contact. After a short time the feather will 
leave the wax and fly back to its original posi- 
tion. Now the motion of the feather, which I 
have been describing, is occasioned by elec- 
tricity. 

If a piece of glass be substituted for a piece 
of sealing-wax, then will the glass also attract a 
feather or other light substance ; but you will ob- 
serve this curious fact, that when the feather is 
tired of remaining in contact with the electrified 
glass, then will it immediately go towards the 
sealing-wax ; from which circumstance it is 
presumed that there are two kinds of electricitv , 



dr. franklin's DISCOVERY. 21 

one from glass, called vitreous, (vltrum being 
the Latin word for glass,) and another from re- 
sinous substances, like sealing-wax, called re- 
sinous. 

The electrical machine is merely a contriv- 
ance for rubbing a large piece of glass by ma- 
chinery, instead of giving one the trouble of 
doing so by the hand. 

I must not forget to tell you that thunder 
and lightning depend upon electricity, nor must 
I omit to mention the means by which the ce- 
lebrated Benjamin Franklin discovered this. 
Certain circumstances led him to believe that the 
phenomena of thunder and lightning depended 
upon electricity ; and he reasoned thus : — 
Electricity will pass through metal, therefore I 
want a piece of metal which shall approach 
very near to a thunder-cloud and reach to the 
earth, when, if electricity be really contained 
in this thunder-cloud I shall bring it to the 
earth. But, thought he, how am I to raise my 
metal high enough ? Thus reasoned the states- 
man and philosopher, Benjamin Franklin. Re- 
mark, now, how cleverly he accomplished his 
purpose : through a long piece of cord he ran a 
very fine wire, and providing himself also with 
a silk handkerchief and two pieces of lath, he 



22 



ELECTRICAL KITE. 



went into the fields on the approach of a 
thunder-storm. When arrrived at his destina- 
tion, he tied his sticks together across each 
other, and straining over them a silk handker- 
chief, he made a kite, to which he attached the 
string and flew it aloft. Very soon a thunder- 
cloud passed over it, and the philosopher plac- 
ing his knuckle near the string, drew an elec- 
trical spark ; thus proving that his suppositions 
relative to the nature of thunder and lightning 
were all correct. 










By this circumstance you learn, that even 
the toys of boyhood may be converted into 
valuable instruments in the hands of a person 
who is really bent upon the study of philoso- 
phy. The experiment of Franklin is exceed- 
ingly dangerous, and one that I would not have 



LIGHTNING CONDUCTORS. 23 

you repeat, since a quantity of electricity might 
pass down the cord quite sufficient to destroy 
life ; indeed, there have already been several 
instances of death occasioned by trifling with 
thunder-clouds. Electricity does not pass 
through all substances with equal facility — 
metals convey it with scarcely any interruption, 
hence they are called conductors ; but glass, 
wax, resin, and silk, together with some other 
bodies, intercept nearly the whole of it, hence 
they are termed non-conductors. 

Tapering above the church-steeple of this 
village is a pointed piece of iron, termed a 
lightning conductor ; it passes down the side of 
the edifice deep into the ground, and its use is 
to protect the building against lightning. If 
the rod were not there, a thunder-cloud passing 
over the steeple might suddenly dart upon it an 
immense quantity of electricity, in the form of 
a flash of lightning, and shatter it to pieces ; 
but the iron would prevent such an accident, by 
conveying the fluid silently, rapidly, and safely 
into the ground. Well, you will always re- 
member that the imponderable substances, or 
those without weight, are 

Light, 

Heat, 

Electricity. 



24 CHEMICAL MANIPULATION. 

The old philosopher, having finished his 
second Lecture, called us around him, and ex- 
plained, that on the occasion of our meeting 
again, he would instruct us in the manner of 
performing chemical experiments, each one for 
himself. " I" said he, " will take my instru- 
ments, and you shall take your instruments; 
that which I do you will imitate, and in this 
manner each of my young friends will speedily 
become an expert chemist." But his descrip- 
tions were so intelligible, that even had he not 
shown us, we should have known what he 
meant. I hope, therefore, that all who read his 
Lectures, and see copies of his drawings and 
instruments, will be able to perform the neces- 
sary experiments without the personal assist- 
ance of the old philosopher. 



25 



LECTURE III. 

EXPLANATION Ol< WHAT IS MEANT BY THE TERM 

WEIGHT PONDERABLE BODIES, OR THOSE 

WHICH POSSESS WEIGHT — SPECIFIC GRAVITY. 

Before I describe to you the nature of ponder- 
able bodies, or those which have weight, it is 
necessary for me to explain what weight is. 
All substances within a certain distance of the 
earth (except light, heat, and electricity) are 
drawn towards the centre of the earth with a 
certain force, and the degree of force with 
which a body is so drawn or attracted is 
termed its weight. Now the further a body is 
removed from the centre of the earth the less 
is its weight ; consequently, as the earth is 
somewhat of this shape,* a 
body at B will weigh less 
)e than a body at A ; therefore 
the weight of a substance is 
less at the equator than at 
the poles. When a stone is thrown into 

* In order to make their remarks more impressive, lecturers 
are very often guilty of exaggeration, which is the case in 




26 GRAVITATION. 

the air it falls again to the ground because 
of its weight. Little do you think that the 
whole earth is moved by the mere throw- 
ing of a stone ; but such is indeed the case. 
The earth attracts the stone, and the stone 
the earth, therefore each moves towards the 
other ; but as the stone is infinitely smaller 
and lighter than the earth, so does it move the 
earth to an equally small extent. A person 
when jumping or dancing moves the earth, 
however little he may be conscious of the fact. 
Perhaps then, in future years, when I shall be 
dead and gone, some of my young friends, 
whilst engaged in the merry dance, may call to 
mind what an old man once told them about 
their moving the world. 

This force which causes bodies to approach 
each other is termed gravity or gravitation ; 
sometimes also it is called the centripetal force, 

the present instance ; for the old gentleman, wishing to 
make his audience remember that the earth is not a perfect 
globe, has represented it in his diagram so enormously flat- 
tened at either pole, that in shape it almost resembles a 
turnip. Now the earth does certainly happen to be a little 
flattened at each pole, yet in a very slight degree, so that 
the diameter of the earth, from pole to pole, is only thirty- 
five miles greater than its diameter at the equator. Al- 
though, then, the old gentleman has chosen to make the earth 
appear so enormously flattened in the diagram, yet the 
reader should remember that, strictly speaking, this is not 
correct. 



GRAVITATION. 27 

because it makes bodies approach each other's 
centres. Gravitation, or the centripetal force, 
and the centrifugal force, acting conjointly, re- 
tain the planetary bodies in their orbits : if 
gravitation acted alone, then those planets 
would all come together. If the centrifugal 
force acted alone, then would they continually 
separate from each other ; but both operating 
together, the planets are made to revolve round 
the sun as a centre. The power of gravitation, 
or the weight of bodies possessing equal 
sizes, is in proportion to their density. An 
orange is much less dense than a cannon-ball 
of equal dimensions, and therefore is much less 
heavy. 

The sun is 137,763 times larger than the 
earth, but his density is only a little more than 
a fourth of the density of the earth ; that is to 
say, if a piece were cut out of the sun equal 
to our globe in size, it would only be one-fourth 
and a little more of the earth's weight ; and, of 
course, all substances on the surface of such a 
body would only weigh a little more than one- 
fourth part of what they do here. However, so 
immensely great is the size of the sun, that 
notwithstanding his diminished density, a mo- 
derate man would weigh on his surface no less 



■28 SPECIFIC GRAVITY. 

than two tons, and consequently would not be 
able to move ; whereas, if placed on the little 
planet Vesta, he would weigh only a few 
pounds, and might probably be blown away by 
the first puff of wind. If, then, you should be 
asked the meaning of gravity or gravitation, 
you would say that it was the force which at- 
tracted masses towards each other ; and if you 
were asked the meaning of the term weight, 
you would say it was the estimation of the 
gravitating force of any body. 

In philosophical books there frequently oc- 
curs the term specific weight or specific gravity. 
I will soon render the subject of specific gra- 
vities intelligible by means of a few exam- 
ples. 

Suppose I weigh any given measure of water, 
say a square-inch, and call its weight one, or 
unity ; after having done this, suppose I weigh 
a square-inch of iron, and find its weight to be 
eight times greater than unity, or the weight of 
an equal bulk of water ; of copper, and find its 
weight to be nine times greater ; of lead, and 
discover that its weight is eleven times greater; 
I should say that the specific gravities of iron, 
copper, and lead were eight, nine, and eleven, 
respectively ; water being one, or unity. Instead 



SPECIFIC GRAVITY. 29 

of taking water for unity, I might have chosen 
some other substance ; but, upon the whole, 
water is most convenient as the unit of com- 
parison for solids and liquids, and atmospheric 
air for gases. If, then, you should be told that 
the specific gravity of a liquid or solid is two, 
three, four, or, in short, any other number, re- 
member that those numbers indicate how much 
heavier a substance is than an equal bulk of 
water. When, however, you hear or read of 
the specific gravity of a gas, remember that its 
weight is compared with an equal bulk of at- 
mospheric air. 

If we could measure out given quantities of 
any substance we pleased, and compare their 
weight with an equal quantity of water, the 
theory of ascertaining specific gravities would 
be very easy ; but we are frequently obliged to 
obtain information in an indirect manner, inas- 
much as it is not always possible to convert a 
body whose specific gravity is required into the 
proper size and shape. The method of taking 
specific gravities of solids and liquids I shall 
describe when speaking of water, and of gases 
when speaking of air. 

I have already mentioned that the ancient 
Greeks and Romans imagined all substances in 



30 EARTHS — COMPOSITION OF. 

nature to be composed of four elements — fire, 
air, earth, and water. Now fire is not an ele- 
ment at all, being merely an effect of certain 
chemical changes ; as to air and water, each is 
composed of two different gases, and earthy 
bodies are made up of the rusts of various 
metals. A chemist, speaking to persons ac- 
quainted with his science, would make use of 
the word oxide instead of rust, but I prefer em - 
ploying the latter term because it is most easily 
comprehended. We speak of iron rusting, and 
of copper and lead tarnishing ; well, this rust, 
or tarnish, is nothing more than an oxide of 
the several metals. Lime is the rust or oxide 
of a metal termed calcium, and magnesia the 
rust, or oxide, of the metal magnesium : now 
lime and magnesia are earths : the mould of 
gardens and fields, which, in common language, 
is termed earth, consists of the real chemical 
earths, mixed with different other substances, 
such as animal and vegetable matters under- 
going decay. 

Potash is the rust or oxide of a metal called 
potassium, and soda of the metal sodium. 
Potash and soda are termed by chemists alkalies. 
In short, there are forty-two metals, each of 
which is capable of crumbling intorustor oxide, 



LIST OF NON-METALLIC ELEMENTS. 31 

either by natural or artificial means, and those 
oxides are possessed of various properties. 

It appears, then, that the ancients knew very 
little of chemistry ; and if they could now re- 
visit the world and see the wonderful discoveries 
which have been made, they would be very 
much astonished indeed. 

There are, I mentioned, fifty-five elements, 
or, as they are sometimes called, simple sub- 
stances, besides the imponderables. If I were 
writing a large book on chemistry I should 
classify those substances, and tell you a good 
deal about each of them ; but now I shall 
merely divide them into the metallic bodies, or 
those which are metals, and the non-metallic, 
or those which are not metals. The names of 
many in both of those classes you have never 
heard of, I shall therefore omit their descrip- 
tion, and only mention such as are best known 
or most interesting. In my next Lecture I shall 
speak of the non-metallic simple bodies indi- 
vidually. They are, 
Oxygen, Bromine, Selenium, 

Nitrogen, Fluorine, Phosphorus, 
Hydrogen, Carbon, Boron, 

Chlorine, Sulphur, Silicon. 
Iodine, 



32 



LECTURE IV. 



OXYGEN. 



The word oxygen is of Greek origin, and sig- 
nifies the acid maker ; so called, because it 
enters into the composition of a great number 
of acids; indeed, once it was imagined that 
every acid contained it, but such is not the 
case. The air we breathe is composed of 
twenty-one parts by measure of oxygen gas, 
and seventy-nine of another gas, called nitro- 
gen ; but oxygen gas is never procured from 
the air, the process being too troublesome. 
There are many ways of getting it, but I shall 
content myself with showing you that process 
which is easiest for you to follow, and which 
affords oxygen gas of the greatest purity. But 
the process requires some instruments, and I 
am going to show you how to make a great 
many of your own. First of all you must pro- 
cure a spirit-lamp ; a piece of small glass tube, 
or pipe, about the size and thickness of a goose- 



CHEMICAL INSTRUMENTS DESCRIBED. 33 




quill, and a glass flask. Now first let me de- 
scribe to you the use of your tools, for you are 
going to work glass. A spirit-lamp is an in- 
strument of this shape, and 
in no respect differs from a 
common lamp, except that 
spirit-of-wine is employed 
instead of oil. Spirit-lamps 
are much used by chemists 
as sources of heat, and are 
very convenient for the pur- 
pose of bending glass. A 
flask is a bottle of this shape ; 
they are used of different sizes. 
Florence flasks, or those which 
come from Florence, in Italy, full 
of olive-oil, are much used in 
chemical experiments ; but for 
your present purpose you do not 
Require a flask which is more 
than an inch in diameter. It 
should be made of green glass ; a substance 
which withstands the application of heat much 
better than that which is white. 

Fit tightly into the mouth of your flask a 
very sound cork ; now take it out, and by means 




34 CHEMICAL INSTRUMENTS DESCRIBED. 

of a red-hot wire make a hole through it ex- 
actly large enough to admit the end of the glass 
tube ;* which being done, you will have formed 
an instrument of this shape — 



however, you do not want it straight, but bent 
like this ; 




therefore you must now light your spirit-lamp, 
and applying the heat gradually to the tube, 
you will find that, after a short time, it bends 
as easily as a stick of warm sealing-wax. 
Now cool it gradually, and you are prepared 
to commence the operation of making oxy- 
gen gas. Into your flask place about half a 
drachm of the substance called chlorate of pot- 
ash, and then insert the bent tube with the cork 

* Corks may be most easily perforated by pressing against 
them, with a rotatory motion, apiece of brass tube filed to 
a sharp edge. 



CHEMICAL INSTRUMENTS DESCRIBED. 35 

attached ; you will have an instrument, or ap- 
paratus similar to this diagram.* 




Now chlorate of potash is a substance that 
contains a great quantity of oxygen in a solid 
form ; and by the application of heat it gives 
off the whole of this oxygen in a gaseous state ; 
consequently, if you make your flask very hot 
by means of a spirit-lamp, oxygen gas comes 
over : but how must we collect it ? you will say : 
I will tell you. Take a basin of water and put 
into it a small bottle, so that the latter may 
also become filled with water ; then invert the 
bottle in such a manner that its mouth may still 
continue under water, and you will have an 
apparatus of this 
form. So long as the 
mouth of the bottle 
remains under the 

* If the flask be small, and not overcharged with ingre. 
dients, its separation from the tube will he amply guarded 
against by the mere pressure of the cork ; if larger and 
more heavy, it may be secured by means of a little thread. 

d2 




36 



PREPARATION OF OXYGEN GAS. 



surface of the water in the basin that portion 
of water which the bottle itself contains will 
not come out. You may now put your appa- 
ratus together, and proceed to collect oxygen 
gas. 




Very soon after the application of heat, the 
chlorate of potash melts ; then boils, and the 
gas which comes over rises through the water. 
You must not collect the first few bubbles, for 
they are contaminated with the air which filled 
the flask and tube ; when those bubbles have 
escaped, put the end of the tube under the 
mouth of the bottle, and gas ascending drives 
the water out, until the bottle becomes what 
you would perhaps call empty, but it is full of 
gas. I shall not now stop to describe the 
changes which have taken place in preparing 
this gas ; however, I will give you a diagram, 
which had better be copied into your note- 



EXPERIMENTS WITH OXYGEN GAS. 37 

books. On some future occasion I will ex- 
plain the nature of chemical diagrams, and 
show you how easily they express changes of 
composition : the theory of the production of 
oxygen from chlorate of potash will then be 
intelligible.* 

C Oxygen --^ (escapes) 

Chlorate f chloric Acid \ ,s 



OF 



* Chlorine , 



i ( Oxygen • 

Potash, r < 

V. Potash ( Potassium ^Chloride of Potassium. 

I now mean to teach you the properties of 
this oxygen gas, and you will require many 
bottles of it: as soon as one is full take it away, 
substituting another in its place. When you 
observe that all the water is driven out from a 
bottle, proceed as follows : — Take a small 
square piece of window-glass, grease it well on 
one side, and place the greased side under wa- 
ter against the mouth of the bottle, which may 
be now taken out and put upon a table. 

Suppose we have an experiment. To one 
end of a piece of copper wire affix about an 
inch of small wax taper, pass the other end 

* On the large scale, oxygen gas is procured from a sub- 
stance called the per-oxide of manganese, either by heating 
it in an iron retort, or by applying heat to this substance, 
mixed with oil-of-vitriol, and placed in a retort of glass. 



t 



38 EXPERIMENTS WITH OXYGEN GAS. 

first through a perforated disc of tin- — . 
plate, just large enough to cover the f ^ \ 
mouth of the bottle, and then into a \^/ 
cork which serves as a handle. After- 
wards bend the wire to this shape. Now 
light the taper, and when the wick has 
become red-hot, blow out the flame, im- 
mediately plunging the ignited wick iuto 
your bottle of gas ; the flame instantly j) 
rekindles, and bums with the most daz- Cg 
zling brilliancy. Particularly remember, U 
that although oxygen gas makes other sub- 
stances burn so very well, still it is quite inca- 
pable of burning itself, therefore, in chemical 
language, it is said to be a supporter of com- 
bustion, but a non-combustible. 

Now place another bottle full of gas on the 
table, for I intend showing you a still more 
wonderful experiment, — the burning of iron 
wire. Twist some small iron or steel wire, (a 
piece of steel piano-string is very good for the 
purpose) around a stick, by which means you 
make a coil something like a cork-screw. Now 
straighten each end of this coil ; prepare one 
end with the disc and cork, as in the last ex- 
periment. To the other end attach, by means 



EXPERIMENTS WITH OXYGEN GAS. 39 

of some still finer wire, (either brass or iron,) 
the point of a brimstone match. 

Now if you light this point, and then plunge 
the whole wire into one of your bottles full of 
oxygen gas, you will be surprised to see the 
wire burn with a brilliancy far greater than 
that of a candle, throwing off the most beauti- 
ful sparks in every direction, while little melted 
globules fall to the bottom of the bottle, which 
will most probably break. 

I wish you particularly to remember one 
thing in connexion with the experiment just 
performed : the globules of melted metal, which 
fall during the process of burning, are found, 
when weighed, to be much heavier than the 
iron from which they are produced; proving 
that the iron during combustion unites with 
something which has weight ; now this some- 
thing is oxygen, which, losing its gaseous state, 
becomes solid. I have already told you that 
rust of iron is nothing more than iron com- 
bined with oxygen : well, besides this red oxide 
of iron, there is another, which when prepared 
by certain methods is black ; the melted glo- 
bules which our experiment has produced, are 
masses of black oxide of iron. 

There are many other experiments which you 



40 EFFECTS OF OXVGEN ON ANIMALS. 

might perform with oxygen gas, but some of 
them are very dangerous, and therefore I omit 
to mention them until all of you become more 
clever at chemical manipulation- This word 
means a handling, and has reference to the 
dexterity with which you use your instru- 
ments. 

If you were to put a mouse into a large bot- 
tle full of oxygen gas, the poor little animal 
would jump about as if it were mad ; not from 
pain but from delight, because the breathing of 
oxygen gas produces a kind of intoxication, or, 
to speak more correctly, acts as an excitant 
to the nervous system. Well, you may now 
form some idea of the general properties of 
oxygen gas, and I just wish you to remark 
what would be the consequence if we were to 
be surrounded with this gas instead of air. 

Tn the first place, then, all living creatures 
would be somewhat in the poor mouse's condi- 
tion ; men, beasts, and birds, would all run 
wild together. The fishes too might grow in- 
sane, so far as I know, for I shall by and bye 
tell you that fishes breathe as well as our- 
selves. 

Again, every thing in nature would burn as 
soon as it acquired a red, or at most a white 



OXYGEN GAS A SUPPORTER OF COMBUSTION. 41 

heat. AVe could not make the poker very hot 
but it would burn ; we could only extinguish a 
candle by cutting off the wick ; and if a house 
should be on fire the consequences must be 
awful indeed, as there would be no means of 
extinguishing the devouring element, the ter- 
rific oxygen would feed the flames on every 
side, and would set at defiance the united ef- 
forts of every engine in the fire-brigade. In- 
deed, the whole world must shortly be in one 
general conflagration, and it has been imagined, 
(not without some shade of probability,) that 
the earth may be consumed in this very man- 
ner at the last day. The atmosphere consists 
of oxygen and nitrogen ; consequently if the 
Divine Author of nature were to take away the 
latter, and to leave the former alone remaining, 
the whole earth must be inevitably consumed. 

I fear, my dear young friends, you will consi- 
der the long directions which I have given you for 
making your own apparatus somewhat tedious, 
but the necessity for my doing so will not occur 
very often. Every chemist should acquire a 
certain kind of dexterity in making his own 
instruments ; if you were to purchase every 
thing you might require, a great deal of money 
would be unnecessarily expended. A really 



42 



PNEUMATIC-TROUGH. 



scientific man will manage to perform his ex- 
periments with such instruments as may lie 
within his reach. There are sold in the shops 
instruments called pneumatic-troughs, which 




are troughs supplied with perforated shelves, 
over the holes of which you may stand inverted 
bottles full of water ; but a basin or finger- 
glass answers very well for all common pur- 
poses ; and if you wish to supply it with a 
shelf, your own ingenuity will soon enable you 
to make one. Again, instead of holding your 
flask all the time the process is going on, mere 
convenience would soon induce you to invent 
some kind of mechanical support to answer the 
same purpose. A piece 
of stout wire with a ring 
at its extremity, capable 
of being fixed at different 
heights, in an upright 
stick, is a very good con- 
trivance ; but if you wish 
to perform your experi- 




OXYGEN EXISTS IN VARIOUS FORMS. 43 

merits before an audience, and to make a grand 
display, then you may purchase chemical stands 
very neatly constructed at philosophical in- 
strument makers. 

It is the oxygen gas of the atmosphere which 
enables fires to burn and animals to live : from 
this latter property it is termed vital air. I 
shall not now speak of the process termed res- 
piration or breathing, for before I do so it is 
necessary that you should be made acquainted - 
with two other elements ; that is to say, nitro- 
gen and carbon : however, I may just arrest 
your attention by remarking that air several 
times breathed is converted into a deadly poison, 
which is neither capable of supporting animal 
life nor of enabling substances to burn. 

Although we can only obtain oxygen in the 
form of gas, yet in combination it may be either 
a solid or a liquid. Rust of iron is merely a 
compound of that metal with oxygen, and 
oxygen exists as a liquid in both water and 
aquafortis. The immense importance of oxygen 
in the economy of nature may be learned from 
the fact, that at least three-fourths of the whole 
world, including its inhabitants, are composed 
of it ; yet so wonderfully has the Creator 
united it with other elements, that all these 



44 EXPENSIVE INSTRUMENTS UNNECESSARY. 

fierce and intractable properties which it ex- 
hibits in an uncombined state, are lost by com- 
bination. 



The experiments which we witnessed in the 
last Lecture so pleased us, that I, as well as 
many of my friends, repeated them at our own 
homes. We now felt convinced that the truths 
of chemistry were not difficult to understand, 
neither were chemical experiments difficult to 
perform. The glittering array of instruments in 
the chemists' and orjticians' shops, had caused 
us to regard chemistry as something far beyond 
our understanding, and we had certainly no 
idea that so many instruments could be made 
by ourselves. The old gentleman having left 
much to our ingenuity, we followed up his sug- 
gestion, and tried to make oxygen by means 
still more simple than the nasi, and tube, and 
basin. One boy, who was more expert than 
the rest, took a piece of glass tube, about six 
inches long, and having closed one end by 
means of a spirit-lamp, he put into the tube a 
little chlorate of potash ; then he applied heat, 
and not only developed oxygen, but succeeded 



EXPENSIVE INSTRUMENTS UNNECESSARY. 45 



in burning a little coil of iron wire in the same 
tube, without using any other instrument what- 
soever. 

When the next lecture-night arrived, we 
found that our instructor had made an increase 
to his stock of apparatus : — there was on the 
table a glass receiver for gas, also a 
pneumatic-trough ; those he in- 
formed us were very convenient ; 
but, if necessary, he could do with- 
out them. " A wide mouthed bot- 
tle," said he, " would answer the 
purpose of a receiver, and a washhand-basin, 
of a pneumatic-trough." 




46 



LECTURE V. 

NITROGEN HYDROGEN. 

The next elementary substance which I shall 
describe to you is nitrogen, meaning the former 
of nitre — also called azote, or the life-destroyer. 

Nitrogen, like oxygen, may exist in the gase- 
ous, liquid, or solid form, when combined with 
other substances, but it can only be procured 
in a separate state as a gas. 

The air which we breathe consists of nitro- 
gen and oxygen gases mixed together in pro- 
portions which never vary ; every hundred 
parts of the atmosphere, by measure, is formed 
of twenty-one of oxygen and seventy-nine of 
nitrogen. I have already told you what would 
occur if our atmosphere had been pure oxygen, 
instead of a mixture of oxygen and nitrogen. 
Nitrogen, as a constituent of the atmosphere, 
may be compared to water in a glass of grog. 
You may smile at my illustration, but, I assure 
you, it is not a bad one. Nitrogen neither 



NITROGEN EXTINGUISHES COMBUSTION. 47 



supports combustion, nor enables animals to 
live. Oxygen would soon drive us all wild, 
and set the world in a blaze. Nitrogen, there- 
fore, is made to form a constituent of the at- 
mosphere, in order to temper down, or dilute 
the excessive strength of the oxygen. 
I now fix a little piece of taper upon 
a large bung, in this manner, and 
having lighted the taper, I float the 
bung upon the water, which stands above the 
shelf of a pneumatic-trough. Over the taper I 
place a receiver full of atmospheric air. 





The candle, you see, burns at first well 
enough ; now the flame becomes more dim ; 
and now is extinguished altogether. It has 
taken away from the air in the receiver the 
greater portion of its oxygen, and therefore 



48 NITROGEN — HOW PROCURED. 

cannot burn any longer. I am leading you, 
then, by degrees, to understand the true theory 
of obtaining nitrogen. Although a lighted 
candle will separate the greater part of the 
oxygen existing in a given quantity of air, yet 
its flame is not sufficiently powerful to remove 
the whole ; there is, however, a substance 
called phosphorus, which bums with such ex- 
cessive vehemence, that by its combustion every 
particle of oxygen is removed. If I perform 
the experiment again, using a little phosphorus 
instead of the candle, every trace of oxygen 
will be removed, and nitrogen will be the only 
remaining gas. 

Phosphorus is a most dangerous substance, 
bursting into flame on the application of a 
temperature not much greater than that of the 
human body. In appearance it resembles wax, 
and is always preserved in a vessel of water. 
Be particularly careful in using this phos- 
phorus ; never touch it with warm hands, and 
if you have occasion to cut it, always do so un- 
der water. After these remarks, you must be 
very clumsy indeed if you meet with any acci- 
dent from phosphorus in preparing nitrogen 
gas. 

I now take a little tin dish, such as tarts are 



NITROGEN HOW PREPARED. 49 

made in, and having floated it in water, I place 
upon it a piece of phosphorus, about the size 
of a large pea. This phosphorus I touch with 
a piece of hot iron, and it immediately begins 
to burn. I now invert over it the receiver, 
which, you observe, becomes filled with white 
fumes : these are produced by a substance 
called phosphoric acid, formed by the combi- 
nation of phosphorus with oxygen. The phos- 
phorus has now ceased burning, and water, 
you observe has risen in the receiver, proving 
that something has been removed, which some- 
thing is oxygen gas. The white clouds of 
phosphoric acid are now being rapidly absorbed 
by the water; indeed while I speak they 
are gone, and pure nitrogen gas alone remains ; 
colourless, tasteless, and invisible. 

C Nitrogen (remains) 

Atmospheric Air-? 

v. Oxygpn 

Phosphorus _^\ Phosphoric Acid. 

Let us now proceed to transfer our nitrogen 
into bottles, that we may try some experiments 
with it. As the mouths of our bottles are so 
much smaller than the mouth of the receiver, 
we will use a funnel for the purpose of transfer- 
ing the gas with greater ease. 

E 



50 NITROGEN HOW PREPARED. 




I would advise you all to turn up your wrist- 
bands and coat-sleeves, for your arms must be 
immersed a little under water. 

You see, I put the bottle under the surface 
of the water, so that it may become full. Be- 
neath its mouth I now place a funnel; and un- 
derneath the funnel I gradually invert the re- 
ceiver. Bubble, bubble, bubble — up goes the 
gas into the bottle, and out goes the water. 
The bottle is now full. 

I place against its mouth a piece of greased 
window-glass, and removing the bottle full of 
gas, I put it to stand on the table. We shall 
each of us require two bottles full of this gas, 
therefore I transfer some more. 

Now take a bent wire and taper, such as you 
used for an experiment with oxygen ; and hav- 
ing lighted the wick, plunge it into one of the 



HYDROGEN GAS. 51 

bottles of nitrogen. Mark what takes place — 
the flame is immediately extinguished. 

Into another bottle let us throw some lime- 
water, and covering over the mouth, we will 
shake it violently. You are expecting to see 
some change ; but there will not be any. I 
wished you to perform the experiment for the 
following reason. Nitrogen is very similar, in 
many of its properties, to another gas called 
carbonic acid. Carbonic acid, however, whitens 
lime-water, although nitrogen does not, and by 
this means one may immediately distinguish 
them. 

If you were to put a small animal, such as 
a mouse or a bird, into a bottle full of nitrogen, 
the poor little thing would immediately die. 
I do not wish you to be so cruel as to perform 
the experiment, but I merely tell you what 
would be the consequence. How different, 
then, is nitrogen from oxygen ! 

Hydrogen. — Water, which was considered 
by the ancients to be an element, in reality con- 
sists of two elements, oxygen and hydrogen. 
It is to the latter substance that I shall now di- 
rect our attention. I am going to describe to 
you a method of proving that water actually 
consists of two gases. There is an instrument 

E2 



52 



WATER — COMPOSITION OF. 



called the galvanic or voltaic battery, much 
used for the purpose of generating electricity of 
a peculiar kind Electricity, you know, is one 
of the imponderables, or substances without 
weight, a substance which I have purposely 
omitted saying much about, inasmuch as its 
consideration will be better adapted for you, 
when you shall have become more acquainted 
with chemical science. Well, then, galvanic, 
or voltaic, electricity separates water into its 
two elements, oxygen and hydrogen. The 
way to proceed I shall now explain to you, by 
means of a diagram. An instrument is required 
of this shape. 

A B 



N- 



'-C^ 




§p5H 



It consists of a glass goblet, perforated on either 
side ; in which perforations are fixed corks, 



WATER — COMPOSITION OF. 53 

and through these corks are passed wires, 
communicating with a galvanic battery. A B 
are two glass tubes, both filled with water, and 
inverted in the goblet, which also contains 
water, and serves the purpose of a pneumatic- 
trough. Now, on passing voltaic electricity 
from P to N a portion of water is decomposed, 
or separated into its elements, oxygen and hy- 
drogen, both of which, in the separate state, 
are gases ; and passing up into the tubes, dis- 
place that part of the water which remains un- 
decomposed. One tube contains oxygen gas, 
and the other tube hydrogen gas. It is found, 
moreover, that the quantity of hydrogen pro- 
duced in this manner is twice as much by 
measure as the quantity of oxygen. Consider 
attentively the description I have given to you, 
and always remember that water can be proved 
to consist of oxygen and hydrogen, in the form 
of a liquid. The plan is far too inconvenient 
for general employment, and I only mention it 
in order that you may be convinced it is pos- 
sible to separate the two elements of water, and 
to obtain each unmixed with the other. 

I can tell you another way of proving the 
composition of water, although not exactly so 
satisfactory as the one just mentioned. If we 



54 GUN-BARREL EXPERIMENT. 

make a gun-barrel red-hot, by means of a little 
chemical furnace, thus, 




and then pour into this gun-barrel a little water, 
hydrogen gas passes over, and collects in the 
bottle B. Now what becomes of the oxygen 
of the water ? Why it unites with the iron of 
the red-hot gun-barrel, and forms the solid oxide 
of iron. 

This also is an experiment which I merely 
wish you to remember, and not to perform ; 
for I made a promise, that in the early part of 
your study there should not be employed any 
charcoal furnaces, or bellows ; — no soiling of the 
hands, hard work, or burning of clothes. 

I shall now show you the process of making 
hydrogen with the greatest ease. Take a pint 
wine bottle, and adapt to its mouth a cork and 
bent tube, in this manner. 



HYDROGEN PREPARATION OF. 55 




The basin with water, and the receiving bottle 
I need not describe to you, their use is quite 
evident without. Now, in order to make hy- 
drogen gas, put into the bottle some pieces of 
iron, such as nails, or, what is far better, some 
pieces of a metal called zinc : next take an 
earthenware jug, and in it mate a mixture of 
one part, by measure, of sulphuric acid, or oil of 
vitriol, and ten parts of water. The process of 
mixing those substances develops a great 
quantity of heat, hence, if you were to add one 
to the other in the bottle, instead of the jug, the 
glass would immediately break. Pour this mix- 
ture over the zinc until the bottle becomes 
about a quarter full ; then immediately replace 
the cork, and you observe that hydrogen gas 
passes through the tube in great abundance : it 
may be collected in a manner precisely similarto 



56 THEORY OF THE PROCESS. 

oxygen. The gas which first comes over we 
will not preserve, because it is contaminated 
with the atmospheric air, originally existing in 
the bottle and tube. If hydrogen were a very 
disagreeable or injurious gas, I should not al- 
low those first portions to escape, but I would 
collect them in a bottle, and empty the bottle 
of its gaseous contents in the open air. 

r Hydrogen (escapes) 

Water < 

(.Oxygen 

Zinc N> Oxide of Zinc. 

Sulphuric Acid — * Sulphate 

of oxide of 
Zinc. 

As we have now obtained several bottles full 
of this gas, let us place them in order upon a 
table, and 1 will show you how to perform some 
very pretty experiments 

In your left hand take up a bottle full of the 
gas, then let an assistant put his hand on the 
glass plate. Now invert the bottle, and let the 
glass plate be gently removed with a sliding 
motion. This being done, raise into it a lighted 
taper, fixed on the end of a wire. 



EXPERIMENTS WITH HYDROGEN. 57 




You see what occurs ; — the gas itself burns at 
the mouth of the bottle with a pale blue flame, 
but the taper is extinguished. By this experi- 
ment you learn that hydrogen gas is a very 
good combustible, but yet is incapable of sup- 
porting the combustion of another body, which 
I need scarcely remind you is quite the reverse 
of oxygen. 

Hydrogen gas is the lightest of all ponder- 
able substances ; this extreme levity we can 
prove by a very simple experiment. All of 
you, I dare say, have blown soap-bubbles, 
by means of a tobacco-pipe. If, instead of the 



58 TRANSFERENCE OF GASES. 

breath, we use hydrogen gas, (which can easily 
be done by means of a bladder and tobacco- 
pipe,) they will ascend with amazing velocity. 

Before this experiment can be performed, 
we must put some hydrogen gas into a bladder. 
You would soon discover the mode of accom- 
plishing this, no doubt; but to prevent all mis- 
takes I will go through the process. Take a 
glass receiver, 




supplied with a brass cap and stop-cock ; also 
get a bladder, into the neck of which is firmly 
tied another stop-cock. By simply turning the 
stop-cock, the receiver, when placed upon water, 
may be made a close or open vessel at pleasure. 
I close it, then, and proceed to fill it with gas, 
just as I would a common bottle. I now dip 
the bladder in water, to render it pliable; 
squeeze out all the air which it contains, and 
by means of a connecting screw I join it to the 
receiver. 



TRANSFERENCE OF GASES. 



59 




Having done this, 1 turn both stop-cocks, and 
press the receiver quite under water ; which you 
see forces the gas into the bladder, and what I 
wished to do is accomplished. I now turn 
both stop-cocks, and unscrew the bladder. The 
tobacco-pipe may be fixed to the stop-cock, by 
winding a little cloth round its stem, and then 
screwing it in. 

It is not very difficult to fill a bladder with 
gas, without either stop-cocks, connecting- 
screw, or brass cap. 

Take a quart wine-bottle, and by means of a 
very shai-p file cut a notch all round it, about 
an inch from the bottom. Now heat a poker 
red-hot, and apply it to the notch ; most likely 
the glass will crack — it certainly will do so if 
you touch the hot part with a wet rag. When 
the crack is once made, by a cautious applica- 



60 



TRANSFERENCE OF GASES. 



tion of the poker you can cause it to extend all 
round the bottle, the bottom of which, of course, 
falls off. Into the neck of the bottomless bottle 
fit a cork, through which make a hole, and in- 
sert a glass tube, or indeed even a goose-quill 
will do. To the other end of the tube, or quill, 
tie a bladder, supplied with a string round its 
neck, to be tightened when necessary. By this 
.simple apparatus one may fill a bladder with 
gas very well ; but as gas-receivers and stop- 
cocks are not exceedingly expensive, you see I 
have provided you with some. 




Well, the bladder is full of hydrogen gas, and I 
now proceed to blow some bubbles, by dipping 
the bowl in soap-suds, then taking it out, and 
squeezing it under my arm. You see how 
rapidly they ascend, proving that hydrogen 
gas is much lighter than atmospheric air. 



BALLOONS FILLED WITH HYDROGEN. 61 




At the philosophical instrument-makers are 
sold little balloons, which, on being inflated 
with hydrogen gas, ascend in a very pretty 
manner. The large balloons which ascend so 
frequently in London, and elsewhere, are not 
usually filled with hydrogen gas, although it is 
the most proper, but with coal-gas, named car- 
buretted hydrogen, because it can be procured 
in such large quantities at much less expense. 

Hydrogen gas will not support animal life, 
yet it does not seem to be positively injurious, 
but merely kills by excluding oxygen. It 
would not do at all, then, for the atmosphere. 

Hydrogen gas burns, but does not support 
combustion. Oxygen gas supports combustion, 
but does not burn. What then would you ex- 
pect to be the properties of a mixture of these 



62 EXPLOSION OF MIXED GASES. 

two gases? Why, clearly, that they would, 
when inflamed, give rise to the most rapid com- 
bustion possible, or, in other words, to an explo- 
sion: they do indeed explode with excessive 
violence, and when mixed in the proportion of 
two parts, by measure, of hydrogen, to one part, 
by measure, of oxygen, the sole result of the 
explosion is water. In philosophical instrument 
shops are sold very thick bottles of 
this shape, for the purpose of ex- 
ploding mixed gases. In vjlace of 
which may be employed a soda- 
water bottle : but the safest plan is 
to blow soap-bubbles with the mixed 
gas, from a bladder, and eitherignite 
them as they ascend, or while they are still on 
the surface of the water. 

This oxy-hydrogen gas can be burned by a 
peculiar mechanical contrivance, which I shall 
by and bye mention, with perfect safety, and the 
flame produces the most violent heat known; a 
heat that is capable of melting, and even burning 
the most refractory substances. Every five parts, 
by measure, of atmospheric air contain one of 
oxygen gas ; therefore two parts, by measure, 
of hydrogen with one of atmospheric air also 
form an explosive mixture. 




HYDROGEN WHEN INFLAMED FORMS WATER. 63 

When hydrogen gas is burned, water is the 
only product of its combustion. This we may 
very easily prove. I take a jet-pipe, or what 
answers just as well, the stem of a tobacco-pipe, 
round which I wind a little cloth, and then at- 
tach it to the stop-cock of the glass receiver, 
filled with hydrogen gas, and standing over a 
pneumatic-trough. Having turned the stop- 
cock, I depress the receiver, and apply a light 
to the flame which issues : it burns, you see, 
with a very faint light, although its flame gives 
out a good deal of heat. Over the flame I in- 
vert a dry bottle, and see how a dew deposits 
on its sides. This dew is water which has been 
formed by the combustion of hydrogen. 




64 MATTER INDESTRUCTIBLE. 

The gas, then, is not destroyed by burning; it 
merely changes its form, by combining with 
the oxygen of the air. And here let me remind 
you, that no element on the face of the earth is 
ever destroyed. Even the process of combus- 
tion, associated as it is from our infancy with 
ideas of loss and destruction, merely causes 
bodies to assume new forms. All the fires ever 
kindled on the face of the earth, since its 
first creation, cannot have made it weigh one 
grain less than when, with verdure all beauti- 
ful, and with beings all happy, it was first rolled 
forth into space by the hands of its Creator. 



65 



LECTURE VI. 



CHLORINE. 



To-day I am going to teach you the mode of 
preparation, and the properties of another sim- 
ple substance, termed chlorine, from its colour, 
chloros being the Greek word for green. 

In a future Lecture I shall describe the metal 
manganese, or manganesum. At present, I 
need merely remark, that this metal unites with 
oxygen in various proportions, forming several 
rusts, or oxides : one is black, and hence is 
usually known by the name of black oxide of 
manganese ; sometimes called, however, perox- 
ide of manganese, from the very great quan- 
tity of oxygen which it contains — per being the 
Latin word for very much. 

Well, in order to make chlorine, I mix toge- 
ther, in a Wedgwood-mortar, equal parts of 
peroxide of manganese and common salt. 
About two ounces of this mixture I put into a 
retort. I also mix in a jug equal parts of oil- 

F 



66 CHLORINE PREPARATION OF. 

of-vitriol and water, stirring them well together 
with a glass rod. 

Before proceeding one step further, remark 
with what scrupulous attention I arrange the 
receiving bottles on the shelf of the pneumatic- 
trough. Here you see I have a bottle, capable 
of holding a quart, with its well-greased glass 
cover lying so near that it may be seized on the 
instant. By the side of this bottle are several 
others, each capable of holding a pint, and their 
greased glass covers are lying in order before 
me. The reason of all this order and precision 
I will very soon explain to you. In preparing 
gases, the first portions which come over should 
never be preserved, because they are always 
mixed with air. When the gas is harmless, like 
oxygen, or when not injurious in a diluted 
state, like hydrogen, then it may be allowed to 
escape into the air; but chlorine is exceedingly 
irritating to the lungs, even if breathed in a 
very small quantity. This large bottle, then, 
is for the purpose of collecting those impure 
portions, in order that none may escape into 
the air. 

Well, you see I have put about two ounces 
of the mixture of salt and black oxide 
of manganese into a half-pint retort, and I now 



CHLORINE PREPARATION OF. 67 

pour upon it enough of the sulphuric acid and 
water to mate it into a thin paste. Observe, I 
shake the retort every now and then, in order 
that the whole of the powder may become 
moist, otherwise on applying the necessary de- 
gree of heat, the retort would certainly be 
fractured. 

Some of my young friends are coughing, I 
hear, which proves that chlorine is already 
coming over, even before the application of 
heat. I now place the beak of the retort under 
the large bottle, and very gradually apply heat, 
by means of a spirit-lamp. Always apply heat 
to glass instruments very gradually, or else they 
break. The gas bubbles through the water in 
the bottle: now it is nearly pure, as r I can per- 
ceive by its colour. My quart bottle is half 
full, and sliding it aside, I replace it by a pint 
bottle. This has filled, and 1 supply its place 
with another, and another, securing each with 
a well-greased glass j)late immediately it is 
full. 

We shall want chlorine for a future experi- 
ment, therefore let us put aside some bottles 
full of it. When you wish to keep gas in bot- 
tles, do not employ fiat glass covers, but actual 
stoppers, well smeared with pomatum, and not 

F 2 



68 CHLORINE — PREPARATION OF. 

only grease them, but also the interior of the 
bottles' necks. 

After chlorine has passed over for some time, 
its supply begins to cease ; and notwithstand- 
ing the application of heat no more gas is 
evolved : when this takes place, the retort 
should immediately be removed, or else some 
water from the trough will pass back upon the 
hot materials, and cause a fracture of the in- 
strument. The retort is to be removed by 
wrapping a piece of cloth round its neck, and 
carrying it carefully away : take care that no 
water trickles from its wet neck upon its hot 
body— this too would cause a fracture. 

In books you will read that chlorine must be 
collected over warm water, because cold water 
absorbs it : it is very true that water does absorb 
nome chlorine, but this is of very little conse- 
quence, as the gas comes over in abundance, 
and when the water has absorbed a certain 
quantity, the objection is at an end. In prac- 
tice I have always found cold water to be more 
convenient than hot, and therefore I recom- 
mend it to you. 

I have made and collected my chlorine; 
now, perhaps, you will do the same, but as our 
stock of retorts is not very large, some of you 



CHLORINE SUPPORTS COMBUSTION. <>9 

must employ Florence flasks and bent tubes, 
which apparatus, indeed, answers just as well 
as a retort. 

1 have now lying before me several bottles 
full of this gas, with which let us try a few 
experiments. 

It will be necessary for me to lower down 
into those bottles different wires, for the pur- 
pose of immersing a lighted taper, as well as 
some other matters. In addition to the tin discs, 
which we have hitherto used, I also employ 
others, made of card-paper and well greased ; 
those I put under the tin ones, in order to pre- 
vent the escape of any chlorine from the bottles. 

Into one bottle of chlorine I lower a lighted 
taper, which is immediately extinguished : 
chlorine, then, is not a supporter of combustion, 
you say : stop a little, and witness the next 
experiment before you make your decision. 
Into another bottle full of chlorine T 
lower a sheet of gold-leaf by means of 
a wire of this shape ; see how vividly 
it burns. Chlorine then does support 
the combustion of gold, although not of 
a taper. Not only does gold burn when 
thus treated ; for powdered antimony or 
powdered arsenic, both of which are 



70 CHLORINE A BLEACHING AGENT. 

metals, burn when put into chlorine. Phos- 
phorus also burns when similarly treated, and, 
indeed, a great number of substances besides ; 
but I shall not show you those experiments, 
for when the metal arsenic is burned in chlo- 
rine, a chloride of arsenic results, which is a 
most dangerous substance if breathed ; and the 
chlorides of antimony and of phosphorus are 
scarcely more innocent. 

Chlorine is a great bleaching agent, and is 
used in great quantity for the purpose of whit- 
ening linen. The process of bleaching was 
formerly conducted by exposing dark cloths to 
the action of air and moisture : when this plan 
was followed, many months were required to 
complete the operation ; now, by employing 
chlorine, a piece of linen may be bleached in 
the space of a few hours. Let us try this 
bleaching property of chlorine. Into a bottle 
full of it I drop a sprig of parsley, made slighty 
moist with water, and covering the bottle over 
let us wait the result : the parsley has already 
lost its beautiful green colour, and will very soon 
become quite white. Water may be made to ab- 
sorb a great quantity of chlorine, the peculiar 
odour, taste, and smell of which it acquires. If 
it be desired to make a solution of this gas, we 



CHLORINE TESTS FOR. 71 

should employ distilled water, because of its 
purity, and all its atmospheric air having been 
expelled by boiling, of course, it has greater 
capacity for other gases. 

Chlorine, whether alone or in soluble com- 
binations, may be discovered by solutions con- 
taining silver. 

To a solution of chlorine in water I now add 
a solution of nitrate of oxide of silver ; (the 
lunar caustic of surgons ;) immediately, you ob- 
serve, there falls down a white, curdy matter, 
which is chlorine, in combination with the me- 
tal silver, called chloride of silver. But silver 
forms a white compound with many other sub- 
stances besides chlorine ; however chloride of 
silver cannot be dissolved in boiling nitric acid, 
although it immediately dissolves in hartshorn, 
this being the distinctive characteristic. 

Those are all the experiments I shall show 
you with chlorine ; for, notwithstanding our 
precautions, some has escaped, and all of us 
are coughing. Strange to say, this very irri- 
tating substance, chlorine, when diluted with 
atmospheric air, is found to do good if breathed 
by persons suffering from diseases of the chest ; 
and we, who now are suffering a little from its 
effects, shall soon find ourselves quite well and 
comfortable. Men who are employed in bleach- 



72 CHLORINE — THEORY OF PREPARATION. 

ing manufactories, and who are obliged to in- 
hale chlorine day after day, suffer very little 
inconvenience from doing so, and are said to be 
scarcely ever afflicted with that terrible malady, 
consumption. 

I have not yet told you the theory of mak- 
ing chlorine, although each of you has gone 
through the process. To describe verbally the 
exact changes which take place in a chemical 
operation is often a tedious affair, and to 
such young chemists as those around me, the 
information, after all, would not be exceedingly 
valuable. Common salt is composed of chlo- 
rine united to sodium, and is therefore called 
chloride of sodium : it is the salt then which 
furnishes chlorine. Those of my friends who 
wish to investigate the matter more deeply, 
and to become profound chemists all at once, 
may examine this diagram. 

Chloride of ( Chlori "e escapes. 

Sodium. | Sodium 

Peroxide of J 0x yg en — iSoda ^Sulphate of Soda. 

Manganese. |p rotoxid 




Sulphuric Acid ' \ Sulphate of Protoxide 

Sulphuric Acid i of Manganese. 



IODINE TEST FOR. 73 

Before concluding this Lecture, I wish to 
mention three other simple substances, iodine, 
bronine, and fluorine, which in some respects 
resemble chlorine. 

Iodine is a substance which, in appearance, 
very much resembles black-lead, or plumbago ; 
its odour is somewhat like that of chlorine. 
When heated, it yields a vapour of a beautiful 
violet colour, from which circumstance it de- 
rives its name 'ioeides, being the Greek term 
for violet. 

I now put a little iodine into a flask, and 
apply the flame of a spirit-lamp ; see what a 
beautiful violet-coloured vapour immediately 
arises. 

Iodine and starch are very delicate tests one 
for the other. Here is some solution of starch 
made with hot water, but which has now be- 
come cold ; to this I add a little fragment of 
iodine, and stir them well together ; see what 
a deep blue colour the mixture has acquired. 
If then I wished to ascertain whether or not a 
mixture contained iodine, I should add a cold 
solution of starch, which, if iodine were really 
present, would certainly be coloured blue. 

Iodine is procured from sea-weeds, but I 
shall not tell you the process, as the informa- 



74 BROMINE. — FLUORINE. 

tion would do you but little good, and you 
would, perhaps, think me a tiresome old man 
for my pains. 

Bromine is an elementary substance which 
is procured from sea-water, and in many points 
of view resembles chlorine and iodine. Bro- 
mine is a liquid of a deep red colour, and pos- 
sessing a very foetid, disagreeable smell ; from 
which property it derives its name, bromos 
being the Greek word for foetid. 

The test for bromine is also starch, which it 
does not colour blue, like iodine, but yellow or 
orange. 

Fluorine is a substance which is procured 
from fluor, or Derbyshire spar : it has only been 
obtained within the last few years, and for my 
part, I have never seen it. Fluorine is repre- 
sented to be a substance which dissolves nearly 
every thing it touches, and which in its general 
relations is similar to chlorine and bromine. 



75 



LECTURE VII. 



CARBON. 



The next elementary or simple substance I 
shall speak to you about is carbon. I have 
already prepared you to expect that chemistry 
will reveal to you many wonders. I have al- 
ready shown you that the simple substance, 
oxygen, may be at one time a gas, at another 
a liquid, and at another a solid ; but now I am 
going to tell you something still more extraor- 
dinary. Charcoal and the diamond are, chemi- 
cally speaking, the same substance : charcoal 
can be procured from spirits-of-wine, from 
rum, or brandy. Charcoal may exist as one 
ingredient entering into the composition of an 
invisible gas, which gas may be got from lime- 
stone, or from the bubbling soda-water and 
sparkling champagne.* Oh ! I might mention 

* '• In order to give some idea of the proportion in which 
carbon exists in different common substances, it may be 
observed, that a pound of charcoal is equal to, and contained 



76 CARBON. ATOMIC THEORY. 

many other extraordinary things ahout this sub- 
stance, but let me explain what 1 mean by 
asserting that charcoal and the diamond are, 
chemically speaking, the same. You already 
know enough of chemistry to be aware that 
the appearance of a substance is no indication 
of its composition. All bodies are believed to 
be made up of little parts or atoms, so small 
that they cannot be seen even by the most 
powerful magnifying glasses ; but which are, 
nevertheless, upon very strong grounds, sup- 
posed to exist. The reason of this supposi- 
tion I shall not now inform you ; but when 
you have made a little further advancement in 
your chemical studies I will. For the present, 
then, remember, we have every reason to sup- 
pose that bodies are made up of little particles 
or atoms, and the theory relative to those atoms 
is termed the atomic theory. 

Now, supposing charcoal and the diamond 
both to be made up of similar atoms, it is easy 
for one to imagine, that in charcoal those atoms 

in rather more than two pounds of sugar or flour, and of 
eight of potatoes or limestone; so that a mountain of lime- 
stone contains the essential element of, at least, an equal 
bulk of potatoes, and of a forest that would amply cover 
many such mountains." — Prout's Bridgwater Treatise on Che- 
mistry, Meteorology, and the Function of Digestion, p. 117- 



DIAMONDS. 77 

may be differently arranged to what they are 
in the diamond, and that consequently one sub- 
stance is beautifully bright and transparent, 
whereas the other is black, dull, and dirty. 

From this, as well as from many other facts, 
you will find that chemistry is well adapted to 
impress on your minds the truth which you 
have so often heard inculcated, that things 
must not always be judged of by appearance. 
It would be profitable for those who are vain 
of jewellery to remember, that the sparkling 
diamonds which bedeck their persons, dug, as 
they have been from the earth, by the labour 
of ill-treated slaves, bought at an enormous 
expense, and polished with the greatest care, 
are still but little removed from so many lumps 
of charcoal, than which, although more elegant, 
they are far less useful. 

The most common way of making charcoal 
is to place sticks in pits dug in the earth, then 
to set those sticks on fire, and afterwards to 
cover them up with turf, by which process they 
are slowly burned, and charcoal remains. To 
perform this burning cleverly requires much 
experience, trouble, and attention. Some per- 
sons are so expert that they can convert an ear 



78 CHARCOAL HOW MADE. 

of com into charcoal, without destroying the 
form of the grain ; or having carved the resem- 
blance of an arrow, feather and all, out of 
wood, they will not during the operation de- 
stroy the part representing the feather. 

The best charcoal, however, is made in 
another manner, by putting billets of wood into 
a large iron retort, which is then made red-hot; 
by this process very pure charcoal remains, and 
vinegar mixed with water, tar, and some sub- 
stances besides, pass over, and are collected in 
a proper receiver. 

You appear astonished at my saying that 
vinegar is procured from wood, but this is the 
source of the very strongest vinegar, called 
pyroligneous acid. Pyroligneoits is a Greek 
word, signifying fire and wood. Well, I shall 
now leave charcoal, and pass on to another 
form of carbon, called plumbago, or black-lead, 
much used for making pencils and for blacking 
grates. Black-lead, then, contains no lead at all, 
but is carbon, almost pure; sometimes, however, 
there is present a little iron. 

I dare say you are tired of charcoal and of 
black-lead, too ; I readily own there is nothing 
very prepossessing in the appearance of either of 



DIAMOND NATURAL HISTORY OF. 79 

them, although both are more useful than the 
much-admired diamond, respecting which I 
have now something to tell you. 

The diamond, called by the ancient Greeks 
adamas, by the Persians almas, and by the 
inhabitants of India heera, has been known 
and valued from a period of very great anti- 
quity. Pliny mentions it as being the most 
valuable of human possessions, and says, " that 
ancient writers desciibe it as found only in 
Ethiopia, between the island Mera and the 
Temple of Mercury." He then goes on to say, 
that " lately it has been brought from India ; 
that it is incapable of being heated in the fire; 
from which property, together with its extreme 
hardness, the Greeks called it adamas, uncon- 
querable." Pliny then tells us, " that naturally 
the diamond cannot be broken into fragments ; 
but this may be done after soaking it in the 
blood of a he goat ! and that the fragments so 
procured are very valuable for engraving on 
other gems. He affirms, that the diamond and 
the magnet have a great antipathy for each 
other, so that the latter cannot attract iron 
when in contact with the former : also that the 
diamond destroys the effect of poisons, and 
cures insanity." Well, really, 1 have hardly 



80 DIAMOND — NATURAL HISTORY OF. 

patience with Pliny for writing such nonsense ; 
you need not be told that the diamond is not 
softened by goat's blood, neither does it cure 
insanity, nor prevent the magnet attracting 
iron. 

We may learn from Pliny, however, one fact, 
that diamonds had not long before his time 
been brought from India. A part of the world 
which furnished the exclusive supply of dia- 
monds from the time of Pliny until the year 
1728, when this gem was found in Brazil. The 
ancients valued diamonds on account of their 
hardness ; the method of giving them a beau- 
tiful polish was only discovered in the year 
1746, before which time they were used as orna- 
ments in their native and unpolished state ; at 
least in European nations : — the inhabitants of 
India possessed the art of giving diamonds an 
imperfect polish at a much earlier period. 

As soon as the Arabians had conquered 
Spain, and had introduced into Europe the 
wild fictions and romantic notions of eastern 
climes, the value of gems increased ; they were 
thought to have an alliance with beings of 
another world, and to be endowed with the 
most extraordinary powers. The diamond in 
all these respects was ranked as pre-eminent ; it 



CELEBRATED DIAMONDS. 81 

was worn on the person as a charm or amulet, 
and was considered to guard its possessor 
against poisons, witchcraft, insanity, and evil 
spirits. 

These superstitious notions (thanks to the 
spread of information) have long since been 
discarded, and we attribute to the diamond no 
such mysterious properties ; still its nominal va- 
lue is just as great as ever. 

As an article of real utility, the diamond is 
of no great importance, its use being chiefly 
confined to the polishing of gems and the cut- 
ting of glass,- — but owing to its extreme beauty 
it is still sold at a most exorbitant rate. 

There is a regular scale of value for these 
gems according to their weight,but it is scarcely 
aj>plicable to very large diamonds, which would 
come to sums so enormously great that no pur- 
chasers could be found sufficiently rich to buy 
them. 

The Pitt or crown-diamond of France, if 
valued according to the strict rule, is worth 
£141,058. It was found at Pasteal in Gol- 
conda, and was purchased by Mr. Pitt, the 
governor of Madras, for a sum equal to about 
£20,000 of our money. In the year 1717, he 
sold it to the Regent of France, as a crown- 

G 



82 CELEBRATED DIAMONDS. 

jewel, but Napoleon had it set in the hilt of a 
sword of state. 

TheEmperor of Austria possesses a very large 
lemon-coloured diamond. It was purchased at 
a stall in the market-place of Florence for a 
few pence, as it was thought to be a piece of 
rock-crystal. 

The Emperor of Russia possesses a large 
diamond, the history of which is very cu- 
rious. It once formed the eye of an Indian 
idol, and a French soldier having taken a fancy 
to it, he became priest to the deity ; in which 
capacity he managed to extract the diamond 
eye, and to replace it with a glass one. Escap- 
ing with his treasure, he sold it at what he con- 
sidered a good price, but which was in reality 
a very low one. The jewel, after passing 
through a great number of hands, was pur- 
chased by the Empress Catherine of Russia, 
who gave a sum of ninety thousand pounds for 
it, besides an annuity of four thousand pounds 
as a further remuneration ! The Great Mogul 
possesses a diamond larger than either of these : 
it is of a rose-colour, and was found in Gol- 
conda, in the year 1550. 

But the largest diamond is in the possession 
of the royal family of Portugal ; its value, if es- 



EXPERIMENTS WITH DIAMONDS. 83 

timated according to the common rule, would 
be nearly two million pounds sterling ! How- 
ever some persons doubt whether it be a dia- 
mond or only a white topaz. 

The diamond is the hardest of all known 
substances, and therefore can only be cut or 
polished by rubbing it against another diamond, 
hence we have the phrase " diamond cut dia- 
mond" when one rogue tries to cheat another. 

Long before people were aware of the dia- 
mond's actual composition, Sir Isaac Newton 
suggested that it might contain combustible 
matter, from observing that it powerfully re- 
fracted, or bent from a straight course, rays of 
Ught. He termed it an unctuous substance 
coagulated. In the year 1763, our celebrated 
countryman Boyle proved that the diamond 
might be converted into vapour by a heat not 
exceeding that required to melt copper. Cosmo 
III., Grand Duke of Tuscany, succeeded in 
burning diamonds by concentrating on them the 
sun's rays by a burning-glass ; and the French 
chemist, Lavoisier, first proved that they con- 
tained carbon. 

Notwithstanding the extreme beauty of the 
diamond, one cannot but feel astonished that 
it finds purchasers at a rate so enormous, es- 

g2 



84 DIAMOND AND CHARCOAL SIMILAR. 

pecially when we remember that this proud, 
this imperial ornament, which has ever occu- 
pied the seat of a diadem, is after all but a 
morsel of charcoal which has been made to 
yield to the rays of the sun and to dissolve into 
a noxious vapour. 



85 



LECTURE VIII. 

SULPHUR SELENIUM PHOSPHORUS — BORON- 
SILICON. 

On viewing those large yellow lumps which 
are lying on the table, your imagination invo- 
luntarily paints to you a bundle of brimstone 
matches, and those poor, unfortunate, squalid 
creatures who carry them about. What is there 
interesting in sulphur ? you say to yourselves — 
why devote our precious time to the study of a 
substance which is used for matches ? Oh ! 
entertain not those thoughts, they are unworthy 
of you all. Sulphur would stand high in the 
scale of chemical interest, as being one of the 
fifty-four simple bodies, had it no further claim 
to our attention ; but besides entering into the 
composition of oil-of- vitriol, the uses of which 
are innumerable, it is employed in bleaching, 
medicine, and war. Without sulphur the ladies 
could not have white straw bonnets, for by it 
are they bleached : without sulphur we could 



86 SULPHUR SOURCES OF. 

neither cure certain diseases nor repel our foes, 
for it is used in medicine, and in the manufac- 
ture of gunpowder ; without sulphur the flint 
and steel would throw their sparks in vain, and 
the cottager's hearth would not be gladdened by 
the blaze of a cheerful fire ; nay, without sul- 
phur, probably, we could not exist, for in small 
quantities it enters (vile as you think it) into 
the composition of our own bodies. 

Sulphur is one of the few simple or elemen- 
tary substances which is found to exist in an 
uncombined state. In the neighbourhood of 
volcanoes vast quantities occur almost pure. 
The best sulphur comes from Sicily, but a great 
deal of it is procured in Cornwall, where it 
exists in combination with various metals, and is 
separated from them by means of heat. Sulphur 
is sometimes melted and cast into rolls, when it 
obtains the name of roll sulphur ; at other times 
it is put into an iron vessel, and exposed to 
heat, which operation causes some of it to rise 
in the form of powder ; this powder is called 
flowers of sulphur, and is by far the purest kind. 

Nearly resembling sulphur in many of its 
properties is the substance called selenium, 
which was discovered by the celebrated Swedish 
chemist, Berzelius. Selenium is so called from 



SELENIUM. — PHOSPHORUS. 87 

selene, a Greek word, meaning the moon : but 
selenium has nothing at all to do with the 
moon ; it derives its name from the following 
circumstance. There is a metal called tellu- 
rium, from tellus, a Latin word, meaning the 
earth ; why so called I am sure I cannot tell — 
chemists are often very fanciful in giving names 
to substances which they discover, and here is 
an instance. Well, this selenium was once 
mistaken for the metal tellurium, and when the 
mistake was discovered, and the new substance 
was found to be different from tellurium, they 
called it selenium, after the moon. Almost the 
only person who prepares selenium is its origi- 
nal discoverer, Berzelius. After some trouble 
I have obtained a very small specimen of it, 
which has come all the way from Sweden, and 
as you observe, is stamped with the name of 
Berzelius. 

Selenium is more curious than important, and 
perhaps you will never see a sample of it again, 
therefore I shall say no more about it. 

The next simple body I shall describe is 
phosphorus, a substance not less curious than 
dangerous. 

Phosphorus was discovered by a German 
chemist, named Brandt, in the year 1677, dur- 



88 PHOSPHORUS — DISCOVERY OF. 

ing his search after the philosopher's stone. 
Brandt told Kraaft of Dresden how to make it, 
but would not communicate the process to 
Kunkle, who, however, set to work and dis- 
covered it himself, and the substance was long 
known by the appellation of KunkeVs phospho- 
rus. In the year 1679 Kraaft took the trouble 
to come over to this country in order that he 
might show a piece of phosphorus to the Bri- 
tish king and queen. Whilst he was here, our 
countryman, Boyle, first saw phosphorus, and 
whether Kraaft acquainted him with the pro- 
cess of making it is not certain ; if not, he must 
have discovered the process himself, for he very 
soon did succeed in preparing it. 

Phosphorus, when pure, is nearly colourless, 
and about the consistency of wax. Its most 
curious property consists in bursting into flame 
by the application of a heat little exceeding 
that of the human body, on which account it 
must be handled with great caution, and never 
be kept out of water for more than two or three 
minutes at a time. 

A piece of phosphorus if carried into a dark 
place emits a faint glimmering light; and if let- 
ters be written, or figures be drawn with this 
substance they shine in the dark : however, I 



rHOSPHORt'S EXISTS IN ANIMALS. 89 

shall not perform the experiment, nor would I 
advise any of you to do so, as the mere friction 
against a hard body is very likely to set the 
phosphorus on fire, and I have seen many a 
frightful accident from this cause. There is a 
method of exhibiting the illuminating property 
of phosphorus with perfect safety. If a piece 
of it be put into a bottle together with sulphuric 
ether, there is obtained a solution, which, if 
rubbed over the face and hands, causes them to 
appear on fire, without the possibility of giving 
rise to an accident. 

Such then are the properties of phosphorus ; 
and who would have dreamed of its existence in 
animals ? not only does it exist in them, but it 
seems absolutely necessary to the higher grades 
of life. United with lime and oxygen in a 
peculiar way, it constitutes the greater part of 
bones, from which it is now almost exclusively 
obtained. In nothing is the power of the Al- 
mighty more evidenced than in gaining his 
ends by means which to us seem least adapted 
to the purpose. If a person acquainted with 
the properties of the fifty-four chemical ele- 
ments had been desired to mention one, which, 
in his opinion, might be least adapted to enter 
into the composition of animal substances, and 



f>0 SILICON. 

especially bones, he certainly would have fixed 
on phosphorus, a substance which is no harder 
than wax, and which bursts into flame at much 
lower temperatures than those which are fre- 
quently experienced by animals. Yet, through 
Almighty power, these characteristics of phos- 
phorus in a simple state are altogether lost in 
the hard, and incombustible phosphate of lime, 
which constitutes the greater part of bony 
matter. 

Boron is an elementary substance, which is 
procured from borax ; it is a solid, possessing 
an olive colour, but I have never seen it, nor 
have most other persons, I believe ; therefore 
let us pass it over. 

Silicon* is an elementary substance which is 
procured from flints. The compounds of this 
substance are very important, and I shall speak 
of them in their proper place ; in its uncom- 
bined state, however, silicon is merely inter- 
esting as a chemical curiosity — so difficult to 
procure that I cannot even show you a speci- 
men. 

* There are some persons who imagine this substance to 
he a metal, and by them it is termed rilhittm. 



91 



LECTURE IX. 

COMPOUNDS OF THE NON-METALLIC SIMPLE SUB- 
STANCES WITH EACH OTHER — OXYGEN AND 
NITROGEN. 

Oxygen and nitrogen unite in six different pro- 
portions to form as many different combina- 
tions. One, however, is regarded by most per- 
sons to be a mechanical mixture, and not a 
chemical compound — I mean the atmosphere. 

THE ATMOSPHERE. 

The atmosphere, or air which we breathe, I 
need not inform you was one of the elements 
of the ancient Greeks and Romans, and its 
compound nature was only demonstrated in the 
year 1774. Now, as to the properties of the 
atmosphere, I need not tell you it is colourless, 
and without tase or smell. From the calcula- 
tion of Dr. Wollaston and other philosophers, 
the atmosphere is presumed to be forty-five miles 
high, or, to speak in other words, the earth is 



92 PRESSURE OF THE ATMOSPHERE. 

supposed to be surrounded with a layer of air 
forty-five miles in thickness; how this conclu- 
sion is arrived at I shall not at present tell 
you, because if I did you could not follow me 
through the calculation. 

In scientific books you will read that the at- 
mosphere presses with a force of fifteen pounds 
on every square inch ; by which is meant, that 
if you could take a tube or pipe, having an 
aperture exactly equal to a square inch in size, 
and if this tube were forty-five miles long, so 
that on fixing it vertically, or upright, one end 
of it might rest on the sea, or on a part of the 
earth level with the sea, and the other end ex- 
tend to the farthest limits of the atmosphere, 
then the quantity of air contained in this tube 
would weigh fifteen pounds. I need hardly 
tell you that a square inch is a square, each of 
whose sides is an inch in size. 

Well, then, a column of air forty -five miles 
high and an inch square weighs fifteen pounds, 
which is equal to the weight of a column of 
water an inch square and thirty-four feet high, 
or a column of the metal quicksilver an inch 
square and twenty-nine inches high : you will 
see the use of this information by and bye. 

Now, if the atmosphere be so heavy it must 



ELASTICITV OF THE ATMOSPHERE. 93 

exert great pressure upon our bodies : I think 
I hear you say to yourselves, — to be sure it does ; 
a moderate-sized man perhaps contains two 
thousand two hundred square inches of surface, 
consequently the atmosphere presses upon him 
with a force of thirty-three thousand pounds !* 
We are all of us, then, subjected to an enor- 
mous weight, without which we, however, 
could not exist, for it prevents the fluids of 
our bodies being dissipated in vapour, when the 
soft parts would dry and crumble into powder. 

I shall now speak of another property of the 
air, — its elasticity. You know very well that, 
by exerting sufficient force, a piece of India- 
rubber may be pulled out to three or four times 
its natural length, but immediately this force is 
removed, it returns to its original dimensions ; 
this property is termed elasticity. Well, the air 
is elastic, and, indeed, so are all other gaseous 
substances. It is very true you cannot grasp 
the atmosphere, and pull it out like you would 
a piece of India-rubber, but you can do that 
which amounts pretty nearly to the same thing. 

Put the neck of a small bottle in your 
mouth, and suck out as much air as you can ; 

* There are some who estimate the atmospheric pressure 
on a moderate-sized man to be forty thousand pounds. 



94 AIR-PUMP. AIR-GUN. 

then, on pulling the bottle suddenly away, you 
hear the air, which had been removed, return 
again to the bottle, with a slight noise. One 
may also by means of the mouth force into the 
same bottle more air than it is naturally capa- 
ble of containing, when, on removing the bottle, 
this excess of air will be heard to escape ; both 
those experiments prove that the air is elastic. 

By means of the mouth, only a small quan- 
tity of air can be removed from a vessel ; but 
there is an instrument, called the air-pump, 
which is capable of removing nearly the whole 
of it, although never quite the whole. 

By a mechanical contrivance, which exerts 
much greater force than can be commanded by 
the mouth, a given quantity, or measure of air, 
may be compressed into a space many times 
less than it occupies naturally, and if afterwards 
allowed to escape, it does so with prodigious vio- 
lence ; — on this principle depends the air-gun. 

I must now request that you will pay great 
attention, for I am going to lead you to some very 
important conclusions, from the facts which we 
have been considering. Since the atmosphere 
is forty-five miles high, and since it presses 
upon every thing with a force of fifteen pounds 
on the square inch, it is quite clear that it must 



BAROMETER. 95 

press upon itself. In order to illustrate what I 
mean, let us imagine that instead of a layer of 
atmospheric air, forty-five miles high ; a heap 
of feather-beds of the same height. Is it not 
certain that the one nearest the ground would 
be pressed upon by the whole which might be 
piled up above it ? Is it not evident, moreover, 
that the lower feather-bed would be pressed 
into a much smaller space than the upper one ? 
or, to speak in philosophic language, would be 
more dense ? Certainly : — well, this is pre- 
cisely the case with respect to the atmo- 
sphere ; the lower part of which is pressed 
upon by the whole of that which is above, and 
consequently is the more dense of the two. 
Hoping that you all understand what I have been 
saying, I shall now proceed to teach you the 
nature of the barometer, which is an instrument 
for ascertaining the weight of the atmosphere. 

About the Barometer. — Do you not remem- 
ber my informing you, whilst we were engaged 
in preparing oxygen, that if you inverted a 
bottle full of water into a basin also containing 
water, the water in the bottle would not come 
out ? Yes, I am sure you remember it; but per- 
haps you do not understand the reason : how- 
ever great the length of the bottle may be, pro- 



96 BAROMETER. 

vided it do not exceed thirty-four feet, still, 1 
say, the water will not come out ; but if the 
bottle were to be longer than thirty-four feet, 
then the water would come out. If instead of 
water we employ the liquid metal, quicksilver, 
then the limit to the length of our bottle is not 
thirty-four feet, but only thirty inches. 

Do not accuse me of talking nonsense — / 
never saw a bottle so enormously long as thirty- 
four feet, or even as thirty inches, and I only 
say what I do in order to make you understand 
a principle. Can you give me the reason of all 
those facts ? No. Then I will tell you. The 
reason why water did not come out of the bottle, 
is because the pressure of the atmosphere kept 
it there : a column of water thirty-four feet 
high, and a column of mercury or quicksilver 
thirty inches high, are each of them equal to a 
column of atmospheric air of the same size, and 
forty-five miles high : therefore it is that the 
columns of quicksilver and of water, of the 
heights just mentioned, are balanced by the at- 
mosphere ; but if they exceed those heights, 
then they become heavier than the atmosphere, 
which will consequently nolonger support them, 
and they fall. When trying to understand the 
mechanism of the instrument, you should look 



BAROMETER. 



97 



at it in its simplest form ; so many additions 
are frequently made to an instrument for mere 
ornament, and so many for slight conveniences, 
that its original character becomes lost. If, for 
instance, I had to explain the mechanism of a 
church organ, my first care would be to inform 
you that those large gilt pipes so conspicuous 
iu front were merely intended for show, and not 
for use. Well, I shall now describe to you a 
barometer in its simplest form. 

Take a thick glass tube, about thirty-five 
inches long, closed at one end, and open at the 
other, fill this tube quite full of quicksilver, and 
also pour some quicksilver into a basin or fin- 
ger glass. Now, having cov- 
ered the open end of the 
tube with your fore-finger, 
invert it into the mercury in 
the basin. When you feel 
that your finger has de- 
scended considerably below 
the surface of the mercury, 
remove it from the mouth of 
the tube, and I scarcely need 
tell you what follows, for of 
course you remember that the atmosphere does 
not support thirty-five inches of mercury, but 

H 




98 PRESSURE OF THE ATMOSPHERE. 

only thirty, consequently the mercury in the 
tube will fall five inches. I have not hitherto 
informed you that although the usual pressure 
of the atmosphere at the level of the sea is fif- 
teen pounds upon every square inch, yet it 
varies a little, being sometimes more, and at 
other times less: when it is more, then will a 
pressure be exerted on the surface of the mer- 
cury in the basin greater than fifteen pounds 
on the square inch, and consequently the mer- 
cury will rise higher than thirty inches in the 
tube. On the other hand, when the atmosphere 
presses less, then will the mercury sink lower 
than thirty inches. I think it was j^roved by 
means of our feather-beds, that if we were to 
ascend a mountain, or to go up in a balloon, we 
should be pressed upon less and less by the at- 
mosphere in proportion as our distance from the 
earth might increase ; therefore, by the same 
process of reasoning, it is evident that if we 
were to take with us a barometer, the higher 
we might go, the lower would the mercury in 
our instrument sink. This is the very way that 
people in balloons manage to ascertain the 
height to which they have ascended ; for the 
rate at which mercury sinks at various heights 
has been determined, and may be seen by in- 



RISE OF WATER IN THE PUMP. 99 

specting a table drawn up for the purpose of 
affording the necessary information. The in- 
strument which I have just shown you how to 
make represents the barometer in its simplest, 
and, indeed, its most perfect form ; all other 
alterations are either for the purpose of render- 
ing the instrument more easy to be carried 
about, or more ornamental. 

The barometer is sometimes called a weather- 
glass, because it is found that the mercurial 
column generally falls when the air contains 
much moisture, and rises when the air is dry, 
hence it becomes, to a certain extent, a foretel- 
ler of rain or of dry weather, as the case may 
be. 

Having said so much about this atmospheric 
pressure, I will relate to you an anecdote re- 
specting its discovery. Cosmo the Second, 
Grand Duke of Tuscany, wished to pump water 
from a very deep well, but having erected his 
pump, it was found that the water would not 
rise. This circumstance very much surprised 
his highness, and he called together the philo- 
sophers, in order that the mystery might be 
solved. Now the hitherto received opinion of 
the rise of water in a pump was, that nature 
abhorred a vacuum : but why, then, should na- 
il 2 



100 TOKRICELLI'S DISCOVERY. 

ture be so unkind to Cosmo, Grand Duke of 
Tuscany ? 

The pump-makers were now questioned, and 
they affirmed that water never would rise more 
than thirty-four feet ; why, they could not tell. 
In this state matters remained, until Torricelli, 
a pupil of the celebrated Galileo, undertook the 
investigation of the subject, and he made the 
important discovery, that just as water could 
not be pumped more than thirty-four feet, 
neither could quicksilver be pumped more than 
thirty inches ; and by this time, if I mistake not, 
my young friends have come to the same conclu- 
sion as did the philosopher Torricelli ; — namely, 
that it is atmospheric pressure alone which 
causes water to rise thirty-four feet in a pump, 
and prevents its rising higher. In order that 
you may more clearly understand what I have 
been saying, I will describe to you those dia- 
grams, which are intended to represent a pump 
in various stages of action.* The sketches 
I now show you represent a pump in its very 
simplest state ; the mere skeleton of a pump, 
so to speak. 

* The pump was unknown to the ancient Greeks and 
Romans, also to the Chinese, Indians, and Egyptians : — in- 
vented hy Ctesibius of Alexandria, 120 years 13. C. 



STRUCTURE OF THE PUMP. 



101 




The parts of a pump are, the piston, or 
sucker, A ; the body of the pump, B ; and the 
pipe, C. The piston or sucker is made of 
wood, covered with leather, and exactly fits the 
body, B ; this sucker has a hole bored through 
it, which is covered by a trap-door, a, called 
a valve : the body of the pump has also a 
valve, b. 

I think, then, that a minute's inspection of 



102 WINDS THEORY OF. 

my diagrams will teach you the mechanism of 
a pump. Having put the piston into the body, 
suppose you press it down to the bottom, what 
is the consequence ? Why, of course, the air 
in the bod}' must escape through the valve, a. 
Suppose you raise the piston again, what then 
will take place ? Why, clearly, the valve, «, 
will close, the valve, b, will open, and more air 
will enter the body of the pump through the 
pipe : well, then, you have been pumping air ; 
but if you had immersed the pipe of the pump 
in water, then you would have pumped water. 
The diagrams 1 have given you illustrate the 
action of a pump much better than I can de- 
scribe it : indeed, were it not for the purpose 
of avoiding a little blunder, I would say that 
the drawings speak for themselves. 

When the air is in motion, then we have what 
is called wind. The nature of winds I think 1 
can explain to you in a very easy manner. On 
a cold day, if you sit in a room which contains 
, a good fire in an open grate, you find that 
through every chink and crevice, such as the 
key-holes, and the spaces between the door and 
doorposts, there blows a cold current of air, or 
wind, called in ordinary language a draft. This 
draft depends on the following circumstance. 



BOILING THEORY OF. 103 

Hot air is lighter than that which is cold, there- 
fore that air which has been made hot by the 
fire rushes up the chimney, and the cold air 
blows in to occupy its place. Well, in like 
manner some parts of the earth are hotter than 
others, consequently there is always a current 
of air rushing from the cold parts of the earth 
to those which are hot ; such natural currents 
of air are not termed drafts, but winds. 

Before leaving the atmosphere, I must just 
explain to you the influence which it has over 
the boiling of liquids Persons are so fre- 
quently' in the habit of seeing water boiled by 
the application of heat, that they imagine arti- 
ficial heat and boiling to be necessarily con- 
nected. No such thing, as I shall presently 
explain to you. 

Boiling is merely the conversion of a fluid 
into steam with such rapidity as to be attended 
with bubbling. Were it not for the atmos- 
phere, all liquids in nature would undergo this 
rapid conversion into steam, or, in other words, 
would boil ; for there does not exist a ponder- 
able substance without some heat, although it 
may appear to us quite cold ; and the natural 
tendency of heat is to cause the formation of 
steam, which would therefore ascend from 



104 USES OF THE ATMOSPHERE. 

water, as well as from every other liquid, were 
it not for the atmosphere, which by exerting 
an immense pressure, keeps this steam down, 
and of course prevents boiling. Liquids then 
may be made to boil by two methods. We 
may either take away atmospheric pressure, 
and allow the natural heat of the liquid to act ; 
or we may add so much additional heat as 
may be necessary to overcome the atmospheric 
pressure; and this you know is the common 
plan. 

Without the atmosphere neither can ani- 
mals live nor fires burn : of all the gases that 
we have hitherto prepared, none could supply 
the place of the atmosphere. Oxygen would 
intoxicate us, and set the world on fire : — 
nitrogen would kill us on the instant when 
breathed ; and how terrible must be the conse- 
quences if we were surrounded with an atmos- 
phere of chlorine ! Yet one word of the Al- 
mighty might do all this ! in an instant he 
might abstract either of the gases which form 
the atmosphere ; or from the mild and useful 
sea-salt, he might let loose the suffocating 
chlorine, which would soon destroy all vegeta- 
tion, and kill in excruciating agonies all breath- 
ing creatures. 



USES OF WINDS. 105 

I need not remind you of the utility of 
winds : they disperse the hovering emanations 
of disease, — they work our mills, — and they 
waft to us the luxuries of foreign lands. From 
the gentlest zephyr that allays the summer's 
heat,, to the terrific hurricane which tears up 
forests in its course, every variety of wind has 
its own peculiar use, and ministers to some 
good end ; but what this use or end may be 
our imperfect understandings cannot always 
discover. The rant emanations from decaying 
animals and vegetables under the influence of 
a tropical sun, may require no less than a hur- 
ricane to sweep them away, whilst the less 
noxious effluvia of temperate climes may be 
dispersed by the gentler breeze. 

The meaning of the term specific gravity I 
have already explained to you ; but again I 
repeat, that it is the comparative weight which 
substances have to each other. Gases are com- 
pared with the atmosphere ; liquids and solids 
with water. If a gas be said to have a specific 
gravity of three, it is meant that a certain quan- 
tity, by measure, of this gas, weighs three times 
heavier than an equal quantity, by measure, of 
atmospheric air. This method of taking the 
specific gravity of gases is easy enough in 



106 SPECIFIC GRAVITY OF GASES. 

theory, but as an air-pump is necessary for per- 
forming the operation, I can only describe it. 
A flask supplied with a stop-cock is first 
weighed, when full of air; afterwards the air is 
removed by the air pump, and the flask is again 
weighed. It is now filled with the gas whose 
specific gravity is to be tried, and once more 
weighed. By the first and second operations 
we learn the weight of the flask, and of the 
air which it contains ; — by the third we ascer- 
tain the weight of the gas which it can hold. 

Suppose the flask when full of air weighs 
ten grains, and when full of gas twelve grains. 
Now if the weight of the flask alone be nine 
grains, it is evident that the gas weighs three 
times as much as an equal measure of air, or, 
in other words, that the specific gravity of 
the gas is three. 

I now conclude the subject of the atmos- 
phere, and when we meet again I will proceed 
with the other compounds of nitrogen and 
oxygen. The first I shall describe is the 
laughing-gas, the experiments with which you 
will find exceedingly amusing. 



LACJGHING-GAS. 107 

As might have been expected, our curiosity 
to witness the effects of the celebrated laugh- 
ing-gas, made us all very punctual in attending 
the next Lecture ; scarcely a person in our vil- 
lage was absent : old and young, rich and 
poor, — all came in expectation of great fun. 
The table was covered with a profusion of 
bladders, which were intended to be filled with 
gas, and then breathed from. The old gentle- 
man himself seemed to be as much pleased as 
his young friends ; his natural grave expression 
of countenance had given place to an arch 
smile, and he seemed to share with us in all 
our glee. For some time before our arrival he 
had been busily engaged in preparing the gas, 
many bladders full of which were already col- 
lected ; but some were empty, in order that we 
might go through the process of filling them 
ourselves. Having put the instruments a little 
in order on the table, he recommenced his dis- 
course. 



108 



LECTURE X. 

PROTOXIDE OF NITROGEN — OTHERWISE CALLED 
NITROUS OXIDE, OR LAUGHING-GAS. 

Besides the atmosphere, nitrogen combines 
with oxygen in five different proportions, to 
form as many different compounds, the compo- 
sition and name of which you may see by this 
diagram. 



Nitrogen. 

14 

14 

14 
14 
14 



Oxygen. 



16 

24 
32 
40 



\ Protoxide of Nitrogen — Nitrous oxide, 

( or, Laughing-gas. 

i Binoxide of nitrogen — Deutoxide of nitrogen, 
f or, Nitric oxide. 

Hyponitrous acid. 

Nitrous acid. 

Nitric acid. 



From which you see that fourteen parts by 
weight of nitrogen may combine with eight 
parts by weight of oxygen ; — with sixteen, or 
twice eight parts; — with twenty-four, or three 
times eight parts ; — with thirty-two, or four 
times eight parts; — and with forty, or five 
times eight parts of oxygen, and form five dif- 



ATOMIC THEORY. 109 

ferent compounds. Now fourteen parts of 
nitrogen will not combine with less than eight 
of oxygen, nor with any number of parts of 
the same substance between eight and sixteen 
— sixteen and thirty-two — thirty-two and forty 
— or, in short, with any other number of parts 
of oxygen besides those which are put down 
in the table. 

There is something very curious about this, 
and philosophers can only account for the fact, 
by supposing that all substances in nature are 
made up of little particles or atoms, so im- 
mensely small thatwe can never hope to see them, 
nor to know their exact weights, although by a 
process of indirect reasoning we may ascertain 
how much heavier one atom is than another. 

For instance, it is found that whenever one 
part by weight of hydrogen enters into a com- 
pound, its place cannot be supplied by less than 
fourteen parts by weight of nitrogen; sixteen 
of sulphur and of phosphorus ; eight parts of 
oxygen, and so on for every other element. 
The atom of hydrogen, then, is said to weigh 
one, that of nitrogen, fourteen ; of sulphur and 
phosphorus, sixteen, and of oxygen, eight. 
Consequently the numbers one, fourteen, six- 
teen, eight, are said to represent the atomic 



110 



ATOMIC THEORY. 



weights of those substances respectively. But 
as we are not quite, although very nearly cer- 
tain about the existence of those little atoms, 
some people think it improper to use the term 
atomic weight, because something that we can- 
not absolutely prove is taken for granted ; such 
persons prefer the term equivalent weight ; 
both expressions however have the same mean- 
ing, and are often used indiscriminately. 

Granting that atoms do exist, let us apply 
the theory to our present subject. As the 
atomic or equivalent weight of nitrogen is 
fourteen, and that of oxygen is eight, we may 
state the five compounds of nitrogen, and 
oxygen as is done in this diagram. 



Nitrogen. 


Oxygen. 






1 
2 
3 
4 

5 


Protoxide of Nitrogen 
Binoxide of Nitrogen- 
Hj'ponitrous Acid. 
Nitrous Acid. 
Nitric Acid. 



According to which statement it appears, 
that the smallest possible quantity of protoxide 
of nitrogen, commonly called laughing-gas, is 
composed of one atom, or equivalent of nitro- 
gen in union with one of oxygen. The smallest 



ATOMIC THEORY. Ill 

possible quantity of binoxide of nitrogen, of 
one of nitrogen combined with two of oxygen, 
and so on. 

Such then is the first outline of the atomic 
theory. 1 have not found an opportunity of 
introducing it before, and, indeed, I had some 
idea of omitting it altogether, lest you might 
be frightened at its long name ; but I think 
you will agree with me in the opinion, that 
there is nothing in the least difficult about 
it. 

If I mistake not, my young friends are ra- 
ther tired of this atomic theory, and they wish 
immediately to set about making the laughing- 
gas. I shall not, however, immediately gra- 
tify their wishes, as it is a maxim with me 
never to sacrifice philosophy to fun, although 
both are very good together. This is especially 
necessary in the present instance, for if you do 
not understand the philosophy of the laughing- 
gas before you breathe it, I am sure you will 
not afterwards ; at least, not during this Lec- 
ture. 

It is composed, then, of one atom of oxygen 
and one of nitrogen, and is named protoxide 
from the Greek word protos, meaning Jirst, 
because it is the first or smallest combination 



112 LAUGHING-GAS HOW PREPARED. 

of oxygen with nitrogen. It cannot be made 
by mixing oxygen and nitrogen together, but 
it is procured by distilling a substance called 
nitrate of ammonia. 

Nitrate of ammonia isa saltcomposed of nitric 
acid and ammonia. Nitric acid is made up of 
nitrogen and oxygen, and ammonia of nitrogen 
and hydrogen. If we apply heat to this nitrate 
of ammonia it is converted into water, and 
laughing-gas, or protoxide of nitrogen: the 
diagram I here give you explains how the 
change is effected. 

C 1. Nitrogen 2. Protoxide of 

\ /: Nitrogen, or 

r\. Nitric Aeid ' 3. Oxygen—. ..•'/ Laughing- 
i V / Gas. 

*- 2. Oxygen. 
1. (atom) Nitrate * 

op ammonia. 

C 1. Nitrogen 
1. Ammonia : 

I 3. Hydrogen 




It appears, then, that on applying heat to 
nitrate of ammonia, water, and protoxide of 
nitrogen, or laughing-gas, are formed. If one 
atom of nitrate of ammonia be employed, then 
we shall get three atoms of water and two of 
laughing-gas. Those diagrams for expressing 
chemical changes are just getting into fashion, 
and they are certainly far more convenient than 
mere words. 



LAUGHING-GAS. 



118 



But I see you are all impatient to set about the 
process, and I will keep you in anxiety no longer. 




Some nitrate of ammonia has already been put 
into a half-pint glass retort, the beak of which 
is placed under the shelf of a pneumatic-trough, 
near a proper receiver. I now apply the flame 
of a spirit-lamp : — already the salt begins to 
melt, and now there escape from it bubbles of 
gas, which rise through the water, and are lost. 
Those first portions of the gas having passed 
away, I put the beak of the retort under the 
receiver, and collect the pure gas which next 
comes over. The nitrate of ammonia is only 
to be kept simmering not violently boiling, for 
in that case a very injurious gas would pass 
over, which may be known by its red colour j 
it is called binoxide of nitrogen 



114 LAUGHING-GAS. 

Laughing-gas supports combustion nearly as 
well as oxygen : on plunging into a jar filled 
with this gas the red-hot wick of a taper, its 
flame is immediately rekindled, and even the 
combustion of iron wire proceeds with just as 
much activity in this gas as in oxygen. I wishyou 
to remark, that the bladders are not attached to 
the stop-cocks themselves, but to brass tubes 
which have a larger bore than stop-cocks, and 
into which the latter can be screwed : the rea- 
son for this is evident ; a person could not 
breathe with the necessary rapidity through a 
stop-cock, its apperture being so very small. 

It is called laughing-gas from the peculiar 
effect it produces when breathed ; not that it 
always causes laughter, but it usually gives rise 
to such whimsical contortions of the features, 
and causes persons to play such ridiculous an- 
tics, that if the operators do not themselves 
laugh, those who look on certainly must : the 
claim then of this protoxide of nitrogen to the 
name of laughing-gas is very fairly earned. 

The person who breathes it must proceed in 
the following manner : — holding his nose tight 
between his fingers and thumb, he must forcibly 
expel from the lungs as much air as he can, 
then he must breathe from, and into a bladder 
filled with the gas until its peculiar effects are 



LAUGHING-GAS. 115 

experienced, which probably may be in about 
half a minute. There should be some person 
standing near to pull away the bladder as soon 
as the lips of the person breathing the gas are 
observed to turn blueish, for it might be dan- 
gerous to persist in the operation after this 
symptom. 

Having proceeded thus far in his Lecture, the 
old gentleman handed round a great number of 
bladders filled with the gas ; and here our 
short-hand writer ceased from his work. Anx- 
ious to enjoy the fun as well as the rest, his 
office of scribe did not hinder him from seizing 
a bladder too: for my part I determined to have 
some amusement of another kind, in witnessing 
the effects produced by the gas upon others, 
without breathing any myself ; and, perhaps, I 
laughed more than either of the breathers. Oh, 
how shall I describe the scene which followed ? 
For one instant, the silence of our Le ture- 
room was only broken by the deep-drawn in- 
spirations of those who were breathing the gas : 
all seemed to be enjoying the extreme of happi- 
ness, they puffed and pulled as if they could 
not get enough. It was, indeed, irresistibly 
ridiculous to see a large room filled with per- 

12 



116 LAUGHING-GAS. 

sons, each of whom was sucking from a blad- 
der, and this alone made me laugh right well ; 
but in another instant began their ecstacies, 
some cast their bladders from them with a jerk, 
and, forgetting the ridiculous figure they made, 
kept breathing laboriously; their mouths thrown 
wide open, and their noses still tightly clenched: 
some jumped over the tables and chairs ; some 
were bent upon making speeches ; some were 
very much inclined to fight; and one young gen- 
tleman persisted in attempting to kiss the ladies. 
I have heard it insinuated that he breathed very 
little of the gas, and that he knew very well 
what he was doing ; but this statement I con- 
sider to be untrue. As to the laughing, I think 
it was chiefly confined to the lookers-on. 

A few minutes served to restore those 
maniacs to their senses, and they felt as if 
nothing had occurred ; for it is a peculiarity 
of this gas, that it does not act like intoxica- 
ting liquors in producing depression of spirits, 
disorder of the stomach, or indeed any other 
unpleasant effects. 

As our instructor had predicted, we did not 
after this exhibition feel very much inclined to 
study philosophy, and therefore the Lecture, 
although short, was brought to a conclusion. 



117 



LECTURE XI. 

BINOXIDE OF NITROGEN, OR NITRIC OXIDE — 
HYPONITROUS ACID — NITROUS ACID — NITRIC 
ACID. 

If my young friends are all recovered from the 
effects of the laughing-gas or protoxide of 
nitrogen, they will now be prepared to follow 
me, in my description of fc'raoxide. 

This also is a gas, and is procured by adding 
nitric acid, commonly called aquafortis, to cer- 
tain metals, of which copper is the best. I now 
place a farthing in a cup, and pour upon it a 
little nitric acid : — see what red vapours imme- 
diately arise ; — I have formed binoxide of 
nitrogen. You think then its colour is red, 
but in this you make a very common mistake ; 
binoxide of nitrogen is colourless, although it 
forms red vapours immediately on coming in 
contact with atmospheric air, or any other gas 
which contains oxygen. I will now make some 
in another manner, and prove to you that it is 
entirely without colour. 



118 BINOXIDE OF NITROGEN. 

I put some small pieces of copper into a re- 
tort, and pour upon them a little nitric acid. 
Having done this, I immerse the beak of the 
retort under water, and apply gentle heat. The 
retort is first filled with red fumes, because the 
gas is mixed with atmospheric air; but those 
fumes soon subside, and binoxide of nitrogen 
may be collected in a proper vessel, quite free 
from colour. 

If to a receiver partly filled with this gas 
some atmospheric air be added, then the red 
fumes will immediately reappear. 

We will just have the theory of making this 
binoxide of nitrogen, and then leave it alto- 
gether. 

/"l Nitrogen — .1 Binoxide of Nitrogen. 

1 Acid C < 2 Oxygen-"' 
V3 Oxygen_ 



3 Copper ^^-3 Oxide of Copper.') 3 ^™^ 



1 of Cop- 
3 Nitric Acid _l w- 

The changes which ensue are represented by 
the diagram. 

It appears that nitric acid is composed of 
oxygen and nitrogen. Copper takes away 
part of the oxygen in order to form oxide of 
copper, and the remaining oxygen uniting with 



NITRIC ACID. 119 

the nitrogen, forms the gas which we are en- 
gaged in investigating. 

How much better are those changes ex- 
pressed by a diagram than by words ! Hypo- 
nitrous acid derives its name from the Greek 
word upo, under, because it contains less 
oxygen than nitrous acid. It is composed of 
one atom of nitrogen, and three of oxygen. 

Nitrous acid is another combination of nitro- 
gen and oxygen, composed of one atom nitro- 
gen, united to four of oxygen. 

The red fumes which are generated when- 
ever binoxide of nitrogen mixes with the at- 
mosphere, consist of hyponitrous and nitrous 
acids blended together; but when either is 
required separately, this is not the process to 
be followed. Hyponitrous acid is procured 
with great difficulty, and when obtained pos- 
sesses very little interest. Nitrous acid may 
easily be obtained by distilling the salt called 
nitrate of lead, but its uses and interest are not 
great. I shall not go through the processes for 
making either of them, but pass on to nitric 
acid, which is by far the most valuable of all 
the chemical compounds formed by the union 
of nitrogen with oxygen. 

Most of you, I dare say, have seen nitric 



120 



NITRIC ACID. 



acid, or aquafortis, although you may be unac- 
quainted with the method of preparing it. Into 
a half-pint stoppered glass retort I put about 
half-an-ounce of saltpetre, the chemical name 
for which is nitrate of potash, and I pour upon 
it half-an-ounce, by weight, of strong oil-of- 
vitriol, which, in chemical language is called 
sulphuric acid. I now place the retort upon a 
chemical stand, and put its neck into a clean 
Florence flask. 




The retort must be made hot and the flask, 
or receiver, kept very cool. For the purpose 
of applying heat I shall use a spirit lamp ; and 
I think the best way of keeping the receiver 
cool is to cover it with blotting paper, which is 
preserved wet by the continual dripping of cold 
water. It does not matter how this water is 
made to drop : I might effect it by squeezing 
over the flask a wet sponge ; but the most con- 



NITRIC ACID. 121 

venient method is to place above it a funnel, 
into the neck of which is inserted a notched cork, 
and which is filled with water; by this little con- 
trivance the flask may be preserved quite cold. 

I now apply to the retort the flame of a spirit- 
lamp, and in a very few minutes nitric acid, or 
aquafortis will condense in the flask. 

Suppose we now have the theory of the pro- 
cess. Saltpetre, or nitrate of potash, is composed 
of nitric acid and potash ; oil-of-vitriol, of sul- 
puric acid and water : sulphuric acid takes 
away the potash to form sulphate of potash, 
and nitric acid passes over in combination with 
water. Aquafortis and nitric acid, then, are 
only two names for the same thing, or, to speak 
more correctly, aquafortis is nitric acid, com- 
bined with water.* 

r Nitric Acid Aquafortis. 



Nitbate of Potash. < 

C Potash 

i Water- 
Oil op Vitriol. \ 

' Sulphuric Acid ^^>- Sulphate of Pota*h. 

There has now passed over as much nitric 
acid as is necessary for our purposes, and we 

• It is impossible to obtain nitric acid in an isolated form. 
It must be combined with something, or else it cannot exist : 
this something may be water. Consequently, aquafortis is 
the simplest form under which we can obtain nitric acid, 
being a union of the actual acid with water. 




122 NITRIC ACID — TESTS FOE. 

will proceed to test it, or to try some of its pro- 
perties. 

In the first place, then, I wish you to observe 
it is very nearly colourless : the aquafortis of 
commerce, I grant, sometimes appears red, but 
this is owing to an impurity; we have suc- 
ceeded in manufacturing a purer article. I 
wish you also to remark that nitric acid has a 
very strong and penetrating smell. 

I now dip into this acid a piece of blue lit- 
mus paper, which you observe is immediately 
reddened : this is a test for acids in general, 
most of which redden litmus paper. 

Here is a little crystal of a substance called 
morphia, on which I drop some nitric acid ; 
see how red the morphia becomes. 

I have, unintentionally, spilt a little of this 
acid on my finger, which will soon be stained 
yellow in consequence : this staining of sub- 
stances yellow is, indeed, very characteristic of 
nitric acid, and is sometimes applied to pur- 
poses which are exceedingly useful. Have 
you not observed those yellow borders which 
surround baize table-covers ? they are produced 
by the action of nitric acid. 

I now drop a little of the acid on a piece of 
copper, and red fumes immediately appear. 



NITRIC ACID TESTS FOR. 123 

You would then be certain that a liquid was 
nitric acid if it stained animal substances yel- 
low, reddened morphia, and produced red fumes 
when dropped upon copper. 

Nitric acid is a substance of great import- 
ance : it is used very largely in medicine and 
the arts ; and without it the scientific chemist 
would be unable to conduct some of his most 
important operations. 



124 



LECTURE XII. 

COMPOUNDS OF HYDROGEN AND OXYGEN — 
WATER, PEROXIDE OF HYDROGEN. 

Hydrogen unites with oxygen in two propor- 
tions, forming two different compounds. One 
is water, or protoxide of hydrogen, and the 
other is called peroxide of hydrogen. I have 
already explained to you how it may be proved 
that water is composed of hydrogen and oxy- 
gen : there is yet another method : a mixture 
of two parts, by measure, of hydrogen with one 
of oxygen explodes on the application of flame, 
with extraordinary violence, and water alone 
results. I have here a soda-water bottle, which 
has been filled over the pneumatic-trough with 
the two gases mixed in proper proportions, and 
corked while under water. I wrap a towel 
round the bottle to guard against an injury in 
case of its breaking, and now, drawing a cork, 
I apply a lighted taper. The mixed gas, you 
hear, explodes with great violence, and water 
is formed ; but this is hardly a fair experiment, 



WATER. 



125 



for the bottle, not long since, was standing over 
the water in the pneumatic-trough, — therefore, 
the moisture which now bedews its internal 
surface may either be water which has formed 
by the combination of the two gases, or water 
which it has acquired from the trough. How- 
ever, I have succeeded in proving one fact, that 
a mixture of hydrogen and oxygen gases ex- 
plodes on the application of flame. In order 
to prove that the result of the explosion is water, 
and nothing but water, an expensive instrument 
is required, which I will endeavour to describe 
by means of a diagram : — ■ 

The vessel, A, is made of very 
thick glass, and furnished with 
a stopper, S, which can be 
pressed tightly down by means 
ofascrew. Into this stopper are 
inserted two wires, W W, one on 
either side, and which commu- 
nicate with the interior of the 
apparatus. It is also furnished 
with a stop-cock, P. By means 
of the air-pump this glass ves- 
sel, A, is deprived of its atmo- 
spheric air, and it is afterwards 
filled with a known quantity of 




126 WATER. 

the mixed gas. The stop-cock, P, being then 
turned, and the stopper, S, being screwed tightly 
down, nothing can escape. But how is the gas 
to be inflamed without opening the vessel ? 
The plan is simple enough : an electric spark, 
which resembles a flash of Ughtning in minia- 
ture, is passed, by means of the wires, directly 
through the gas, which consequently inflames, 
and water is deposited on the sides of the ves- 
sel. This experiment is quite satisfactory, for 
it may be proved that the weight of the water 
formed is precisely equal to the weight of the 
gases employed; and as the vessel is filled with 
gas without the aid of a pneumatic-trough, no 
fallacy can arise on this score. 

Three-fourths of the globe on which we live 
are composed of water ; and the great excess 
of this fluid has called forth from Delabeche, 
the geologist, the following remark — that the 
dry land of the earth can only be regarded as 
so many points, which, for the time being, are 
above the water, below which they may at some 
future period descend: or, in other words, if all 
the dry land of this world were made level, 
then would the water be sufficient to cover it 
quite over. Water is said to be without colour, 
taste, or smell ; but this is an incorrect state- 



WATER NOT WITHOUT SMELL AND TASTE. 127 

ment. Small quantities of water certainly do 
appear colourless, but in large masses it has a 
greenish hue, as may be seen in the ocean, also, 
to a less extent, in lakes and rivers. I think, 
too, that water possesses a taste ; and as to its 
being without smell, the assertion may be true 
so far as human beings are concerned, but it 
is mentioned, on very good authority, that the 
camel, when travelling over the burning sands 
of eastern climes, will scent a spring of water 
although many miles away. 

Pure water, then, is composed of hydrogen 
and oxygen ; but naturally water cannot be 
found in a pure state. Sea-water contains com- 
mon salt, besides many other substances ; and 
spring or river-water, although much less im- 
pure than sea-water, is still far from pure. 
When I make use of this term pure, do not 
fancy for a moment that the water which we 
every day use is improper, or that purer water 
would better answer the purposes of domestic 
life ; far from this, neither man, animals, birds, 
or fishes could exist if the earth were entirely 
supplied with water quite pure. 

The purest kinds of water that exist natu- 
rally are melted snow and rain water, both of 
which are very insipid to drink. The chief im- 



128 WATER NEVER NATURALLY PURE. 

purities of water are atmospheric air and car- 
bonate of lime, held in solution by carbonic- 
acid gas. I dare say you have often observed 
what a coating the tea-kettle acquires after 
having been used some considerable time ; this 
coating or crust is nothing but chalk or carbo- 
nate of lime, which deposits as soon as the 
carbonic-acid gas which held it in solution, is 
dissipated by boiling. All gaseous substances 
are capable of being absorbed by water to a 
greater or less extent ; you will have no diffi- 
culty, then, in comprehending how it is that 
water absorbs a greatsr quantity of the atmo- 
sphere, as well as of the gas which is always 
mixed with the atmosphere ; I mean carbonic 
acid. The other impurities of water are col- 
lected from the earth through which it runs. 
By the process of boiling water is deprived of 
its atmospheric air, and rendered flat, disa- 
greeable, and difficult of digestion. It appears, 
then, that atmospheric air is a necessary impu- 
rity ; and those persons who drink boiled water 
under the impression that it is conducive to 
health, act in direct opposition to a wise pro- 
vision of nature. 

Fishes can no more live in boiled water than 
we can exist without air, for these creatures 



MINERAL-WATERS. 129 

require air just as we do ; only they breathe 
air which is dissolved in water, whilst we, and 
other terrestrial animals, breathe that which 
exists in a gaseous state. The gills of fishes 
are the representatives of lungs in land-animals, 
and just as gills can only perform the act of 
respiration in water, lungs can only perform the 
same act in the atmosphere. When water con- 
tains impurities of an unusual kind, and in large 
quantities, then it is termed mineral- water: the 
ocean may be called an enormous collection of 
mineral-water. Bath, Harrowgate, Tunbridge- 
wells, and Cheltenham are all celebrated for 
their mineral-waters. 

By means of its tributary streams, the ocean 
has continually pouring into it large quantities 
of decaying substances, and without its saline 
ingredients it would speedily becomes mass of 
putridity. The salts which it contains also in- 
crease its power of supporting weights, and hence 
render it better adapted for the purposes of navi- 
gation than it otherwise would have been. It 
is quite impossible to contemplate those facts 
and not be struck with the wisdom and the 
goodness displayed in that act of Providence, 
which made the ocean salt instead of fresh. 

K 



130 DISTILLATION EXPLAINED. 

Whenever water is used for chemical pur- 
poses it must be pure, and common water is 
made so by distillation. Of course, you know 
that boiling-water gives off steam, and that this 
steam, if cooled sufficiently, becomes water 
again. Now let us refer to the circumstances 
of the encrusted tea-kettle. All the water which 
was in this kettle has by heat been converted 
into steam, or, in common language, has boiled 
away, and (mark what comes next) has left 
the chalk behind. Suppose, then, that instead 
of allowing the steam to fly away we had cooled 
it into water ; why is it not evident that the re- 
sulting water would have been quite pure ? The 
process of boiling would have driven off all 
its gaseous impurities, and chalk and every 
other fixed impurity would have remained be- 
hind. 

If, then, you wish to obtain pure water, take 
a tea-kettle, and pour into it some common 
water, taking care that it do not rise so high as 
the internal surface of the spout. Now put on 
the cover of the kettle, and make it quite close 
with a little wet clay ; this being done, fix into 
the spout a cork and glass tube thus. 



DISTILLATION HOW CONDUCTED. 



131 




On boiling the water in the kettle, it is quite 
clear that all the steam which arises must pass 
through the tube ; which being cooled by the 
application of moistened pieces of blotting- 
paper, pure water trickles into the basin. 

The operation you have been performing is 
called distillation, and I have directed you to 
employ a tea-kettle for mere simplicity.* Dis- 
tillation may be conducted by retorts, by flasks 
and tubes, and by stills, which are instruments 
of this form : — 



* After considering what has been here stated many 
other simple instances of distillation will present them- 
selves to the reader. 

k2 



132 DISTILLATION — HOW CONDUCTED. 




Instead of cooling the result of distillation 
by means of wet blotting-paper, those who 
conduct the process on a large scale have other 
contrivances. In some cases they employ an 
instrument called a worm, which is merely a 
tube coiled many times round the inside of a 
tub filled with cold water in this manner. 




At other times they use a receiver, precisely 
similar in appearance to a Florence flask, only 
much larger ; on this receiver a stream of cold 



CLOUDS RAIN HAIL. 133 

water is continually made to fall, by which 
means the vapour inside it is condensed into a 
liquid. 

The heat of the sun causes immense quan- 
tities of water to rise in the form of steam or 
vapour : this vapour may exist in the atmo- 
sphere either in a visible or invisible state ; if 
visible, it forms a cloud. When the atmosphere 
is saturated with visible vapour, this, by the 
operation of many causes too numerous for me 
here to mention, is made to assume the condi- 
tion of drops, which descend to the earth in 
the form of rain. Snow is frozen watery va- 
pour, and hail is frozen rain. Water from the 
clouds in either of those forms, after fertilizing 
the barren land, and covering the parched mea- 
dows with a carpet of green, sinks through 
little crevices in the earth, and appears to be 
lost : but soon it bursts forth in the form of 
bubbling springs, which roll down the sides of 
mountains and hills, to unite and form rivers in 
the valleys beneath. Those rivers, pursuing 
their course along the deepest levels of the 
earth, adorn, enrich, and fertilize the regions 
through which they pass. Some, gliding quietly 
on, seem made but to support the heavy ship ; 
others seem created for terror alone, and de- 



134 SPECIFIC GRAVITY. 

scend in roaring cataracts from their mountain- 
beds ; while the rivers of Devon dance over 
the mossy rocks, and sparkle in the sun, as if 
nature had not intended them to carry burdens, 
or to perfom any other hard labour, but merely 
to bathe the flowers on their banks, and to 
adorn the beautiful groves. 

Water is the standard of specific gravity 
for fluids and solids, as I before told you. Tf 
we had to take the specific gravity of a solid, 
with whose exact size you were acquainted, 
such, for instance, as a piece of lead which had 
been cast into a pint measure, of course, we 
might compare its weight with that of a pint 
of water ; but it would be useless to attempt 
proceeding in this manner with a substance 
whose exact size was unknown : let us suppose 
a shilling, for example ; we could not take a 
sheet of water and carve it so that its size might 
exactly equal the size of a shilling ; this would 
be impossible ; and yet, before we can take its 
specific gravity, we must ascertain the weight 
of a quantity of water exactly equal to it in 
size ; how then are we to proceed ? That 
which cannot be effected by direct means, may 
sometimes be. accomplished by those which are 
indirect, as you have already experienced in 



ANECDOTE OF ARCHIMEDES. 135 

many of your chemical operations. The method 
of taking the specific gravity of solids is now 
known, and is therefore not difficult; but its 
discovery was only made by keen reasoning 
and deep reflection. There is a very pretty 
anecdote connected with this subject, which 1 
will relate to you. 

A king of Syracuse delivered to his gold- 
smith a certain weight of gold, for the purpose 
of having a crown made with it. The crown 
was made, and its weight equalled that of the 
gold delivered ; but, nevertheless, the king be- 
lieved it to contain some base metal, which was 
thought to have been substituted in place of the 
gold. How was this to be discovered? Gold was 
known to be heavier than any other metal, con- 
sequently a golden crown of a certain weight 
must necessarily be smaller than a crown of 
the same weight made of any other metal. 
But a crown is a very ornamental affair, co- 
vered with embellishments and carving ; it 
would have been impossible to have measured 
every little inequality on its surface, and 
even supposing this accomplished, another 
crown of pure gold and of equal size, must 
have been constructed for the sake of compa- 
rison ; in fact, the project would have been 



136 ANECDOTE OF ARCHIMEDES. 

hopeless. What then could be done ? The so- 
lution of the problem was entrusted to Archi- 
medes, the celebrated philosopher of Syracuse, 
who attentively considered the subject, and ob- 
tained the necessary information in a very cu- 
rious manner. One day, on entering a bath full 
of water, he found that some ran over; of course, 
any one might have remarked that. He also ar- 
rived at the conclusion that the quantity of water, 
by measure, which ran over must exactly equal 
the size of that part of his body which was 
immersed. Well, then, a golden crown of a 
certain weight must displace less water than a 
crown of base metal of the same weight, be- 
cause it is smaller. Archimedes could wait no 
longer ; his emotions overpowered him, and 
rushing naked from the bath into the streets of 
Syracuse, he ran wildly along, saying, " I hare 
found it ! I have found it /" and indeed so he 
had ; for the king's crown was discovered to 
be larger than it ought to have been, from the 
fact of its displacing a greater quantity of water 
than an equal weight of gold was capable of doing. 
The investigation of Archimedes did not 
cease here ; pursuing his inquiries still further, 
he discovered that a body on being immersed 
in water, not only displaced a quantity equal 



SPECIFIC GRAVITY OF SOLIDS. 137 

to its own size, but that it was pressed up, and 
lost, for the time being, so much of its weight 
as was precisely equal to the weight of the 
water displaced. In this manner we can ascer- 
tain, by an indirect method the weight of a 
bulk of water, corresponding in size to any 
solid whatsoever, no matter how irregular in 
form. 

I have here a piece of lead which I weigh 
in the air, and find its weight to be twenty-two 
grains ; I now weigh it in water by means of 
this contrivance, 




and its weight is only twenty grains ; conse- 
quently the loss is two grains, and is exactly 
equal to the weight of that quantity of water 



138 



SPECIFIC GRAVITY OF LIQUIDS. 



which corresponds to the lead in size. By 
means of a simple rule- of- three sum, I obtain 
all the remaining information which is neces- 
sary. 



Loss sustained by 
lead when weighed 
in water, or weight 
of so much water as 
equals it in size. 



Weight of Water 

lead in air. | taken as one 
or unity. 



Specific 
gravity 
of lead. 



22 



11 



The specific gravity of lead, then, is eleven ; 
that is to say, it is eleven times heavier 
than an equal bulk of water. The method of 
taking the specific gravity of liquids is not so 
complicated ; you would proceed as I directed 
for ascertaining the specific gravity of gases, 
only you neither want an air-pump nor a flask 
with a stopcock, but merely a plain flask, or, if 
you please, a common phial. 

Supposing that your phial is large enough to 
contain 900 grains of a certain fluid, but only 
300 grains of water; then the specific gravity 
of the fluid would be 3, as may be seen by this 
rule-of-three sum : 



300 



900 



But even this calculation, trivial as it is, may 



SOPORIFIC EFFECT OF THE LECTURE. 139 

be avoided, by means of an instrument called 
the thousand-grain bottle. It is a stoppered 
phial, which is known to be capable of exactly 
containing a thousand grains of water : now, 
suppose I fill it with a liquid of which it is ca- 
pable of holding three thousand grains; without 
the aid of any calculation whatsoever, I should 
immediately know that the specific gravity of 
this liquid was three. So much, then, for spe- 
cific gravities. 



The long discourse about specific gravities 
was allowed to proceed amidst the most pro- 
found silence. Our Lecturer warmed as his 
subject progressed ; and, gaining fresh energy 
with every word, he regarded the silence as a 
mark of extreme attention. Poor old man ! 
imagine his surprise when, on breaking the 
thread of his discourse for an instant, to take 
breath, and looking round, he saw, or thought 
he saw, more than half of his audience asleep. 
Wiping the glasses of his spectacles, he took 
another glance, and was not deceived : more 
than half really were asleep. His mouth 



140 ANNOYANCE OF THE LECTURER. 

opened ; his lips quivered ; his eyebrows were 
arched, and a blush passed over his cheek. 
Scratching his ear with his little finger, he bore 
the appearance of one who was vexed at having 
spoken for a long time to little purpose. Slowly 
raising a ruler to the height of his nose, he let 
it fall on the table with a sharp tap, the sound 
of which in an instant aroused the sleeping 
philosophers, who, sitting erect, passed their 
fingers across their half-closed eyes, and by 
straining their lips over their teeth endeavoured 
to conceal those yawns which could not be 
suppressed. The old gentleman looked at 
them for a moment with an expression more 
sorrowful than angry ; pushed his spectacles 
further on his nose ; took a pinch of snuff ; 
made a low bow ; walked as far as the door ; 
opened it ; looked back, and said with a sarcas- 
tic, but not very ill-natured smile, " So much, 
then, for specific gravities !" 

Had it not been that he was annoyed, I be- 
lieve our instructor would have mentioned an- 
other compound of oxygen and hydrogen, 
called the per-oxide of hydrogen. It contains 
an equivalent or atom more of oxygen than 
water, and, like it, is a colourless liquid ; but I 



PEROXIDE OF HYDROGEN. 141 

do not think this peroxide of hydrogen has ever 
been made in England, nor has it been- yet ap- 
plied to any useful purpose, although well 
adapted for restoring the faded white of oil- 
paintings. 



142 



LECTURE XIII. 

COMPOUNDS OF OXYGEN WITH CHLORINE — 

IODINE BROMINE — CARBON, CARBONIC OXIDE, 

CARBONIC ACID. 



Oxygen unites with the simple substances 
chlorine, iodine, and bromine, in several pro- 
portions, to form various compounds, some of 
which are exceedingly dangerous, and none are 
of very great importance ; I shall therefore omit 
their consideration, and pass on to the combi- 
nations of oxygen with carbon. 

Oxygen and carbon unite in two different 
proportions, and form two different gases, which 
are called respectively carbonic oxide and car- 
bonic acid. By inspecting this diagram you 
will see the relative quantity of oxygen and 
carbon in each. 



Carbonic Oxide. 
Carbonic Acid. 


Parts by Weight. 


Atoms. 


Oxygen. 


Carbon. 


Oxygen. 


Carbon. 


8 


C 


1 


1 

1 


16 


6 


2 



CARBONIC ACID. 143 

From which table it appears that the atomic 
weight of carbon is equal to six, and that of 
oxygen to eight. That carbonic oxide is com- 
posed of one atom of carbon united with one of 
oxygen ; and carbonic acid of an equal quantity 
of carbon with two of oxygen. I shall only 
speak about carbonic acid, because carbonic 
oxide is neither a very common nor a very im- 
portant substance. 

All of you know, I dare say, how very dan- 
gerous it is to sit in close rooms where charcoal 
is undergoing combustion, because the sur- 
rounding air is rendered impure. The reason 
is this : charcoal, by the process of burning, 
unites with some oxygen from the atmosphere, 
and forms the very poisonous gas, carbonic acid, 
which contaminates the air. This is the same 
gas which also flies off" from soda-water, cham- 
pagne, and various other liquors, to all of which 
it imparts a peculiar freshness. Carbonic acid 
is also generated in large quantities by the 
breathing of animals. You see, then, that the 
burning of charcoal and the breathing of ani- 
mals both generate the same poisonous gas. 

It seems extraordinary to you, 1 dare say, 
that living creatures can manufacture, by breath- 
ing, a gas which contains carbon, or the matter 



144 PURIFICATION OF THE BLOOD. 

of charcoal. To a chemist, however, the cir- 
cumstance is by no means surprising : our 
bodies are in great measure made up of this 
carbon or matter of charcoal ; a pound of dry 
flesh containing, at least, half-a-pound of it. 
Carbon, although necessary to the animal eco- 
nomy when in a certain proportion, becomes 
injurious if this quantity be exceeded. For 
the purpose of setting free this excess of car- 
bon from the bodies of animals, nature has de- 
vised several processes ; the most important of 
these is respiration, or the function of breath- 
ing. 

Venous blood, or that which circulates in 
the veins, is rendered impure by the presence 
of carbon, or the matter of charcoal, which 
gives it a black colour, and renders it unfit for 
the purposes of life. This carbon, or charcoal, 
nature wishes to separate ; and now remark 
the beautiful contrivance which she employs. 

All animals have some provision for the puri- 
fication of their blood by means of air. In 
man and the higher animals the scheme is as 
follows. There are placed in their chests two 
organs, called lungs, which in texture very 
much resemble a piece of sponge, and into 
which all the blood in the body is frequently 



RESPIRATION. 145 

forced, or squeezed by the contraction of the 
heart, just as water may be forced by the action 
of a syringe into a piece of sponge. By the 
act of inspiration, or drawing breath, air also 
enters the lungs, and its oxygen combining with 
the carbon of the impure blood, forms carbonic 
acid : — the same gas which is produced by the 
burning of charcoal. 

We cannot reflect for an instant on this sim- 
ple yet beautiful means of purifying the blood, 
without entertaining feelings of wonder and 
admiration, for the wisdom, goodness, and 
power of the Creator ; but the first outpourings 
of our gratitude and admiration are scarcely 
over, when we notice an apparent defect. If 
all breathing creatures are so continually gene- 
rating a poison, the whole atmosphere must 
eventually become incapable of supporting life: 
we shall one day, perhaps, be suffocated — this 
carbonic acid will kill us : such, I say, are at 
first our fears ; but they are ungrounded. The 
Creator has devised a means for purifying the 
atmosphere, no less beautiful than that for puri- 
fying the blood ; it is this : — carbonic acid, al- 
though a poison to animals, is a nourishment 
to plants ; the leaves of which having absorbed 
the gas, retain carbon, and set oxygen free in 

L 



146 RESPIRATION. 

all its original purity. The leaves of plants, 
then, correspond in some measure to the lungs 
of animals ; and not only in this, but in many 
other instances, we find in examining the func- 
tions of vegetables, those which correspond 
with functions of animals. 

The atmosphere is poisoned by the act of 
respiration in two ways. In the first place, 
oxygen is removed from the atmosphere, to 
from a component of the noxious carbonic 
acid; and, secondly, nitrogen, itself a poison- 
ous gas, is left behind in a separate state. There 
is this difference between the properties of car- 
bonic acid and nitrogen gases. Carbonic acid 
is a positive poison, whereas nitrogen merely 
poisons by excluding oxygen. To be a little 
imaginative, then, let us suppose that each of 
those gases is a man, and a murderer. Carbonic 
acid lays violent hands upon his victim and 
kills him at once ; but nitrogen starves his vic- 
tim to death, by excluding all nourishment. 
This example illustrates the difference which 
exists between a positive and a negative poison. 
I must tell you, however, that carbonic acid is 
only a poison when breathed : we take a great 
deal of it into the stomach in soda-water, gin- 
ger-beer, champagne, ale, and cyder ; not merely 



CARBONIC ACID. 147 

with impunity but with positive benefit. Car- 
bonic acid exists in many substances as a solid ; 
I may give as examples limestone, chalk, and 
marble, from which it may be driven off by the 
application of sufficient heat, when pure lime 
remains. This is, indeed, the usual method of 
preparing lime ; and you will now experience 
no difficulty in understanding the reason why 
it is so dangerous to sleep near lime-kilns. I 
once remember the circumstance of a poor 
beggar boy who was killed in this manner : 
weary with travelling, cold, pennyless, and des- 
titute, he approached a lime-kiln for the sake 
of its warmth, and laid himself down to sleep. 
Poor little fellow! he slept to wake no more; 
next morning he was discovered quite dead and 
stiff. 

Carbonic-acid gas is also generated in large 
quantities during the fermentation of certain 
liquids. Brewers' vats, for instance, are very 
often full of it, and when in this condition, the 
person who might be unfortunate enough to 
enter one of them would, most certainly, lose 
his life. 

Carbonic acid very often exists in pits ox- 
caves, both natural and artificial. You have 
heard, I dare say, of the celebrated Grotto 

l2 



148 



GROTTO DEL CANE. 



Del Cane, or Grotto of Dogs, near Naples, 
where dogs and other animals are killed merely 
to gratify the curiosity of travellers. It con- 
sists of an excavation in the side of a hill, and 
is represented by this drawing. 

- f. ' 




Into this excavation, carbonic acid pours 
through fissures or chinks in the rock, and 
covers the bottom of the grotto to the extent 
of three or four feet, but no more ; for I should 
tell you that carbonic-acid gas is exceedingly 
heavy, and for that reason can never rise high 
enough to kill a man, although a poor dog, 
whose nose must remain below the deadly at- 
mosphere, immediately falls down suffocated, 
and very soon dies, if he be not speedily thrown 
into water, which generally restores him. The 
guide who exhibits this grotto magnifies the 



UPAS, OR POISON-TREE. 149 

wonder a great deal, by affirming that an ani- 
mal which has been stupified in the grotto can- 
not be recovered by immersion in any other 
water but that of the late hard by ; however, 
if any of my young friends should in after 
times visit the Grotto of Dogs, they may per- 
haps remember that the guide's statement is 
false. 

Most persons have heard of the dreadful Upas, 
or poison-tree, of Java, a tree that was reported 
to spring up quite alone in a valley, spreading 
death and desolation all around it, for a space 
of fifty miles ; which was said to be covered 
with thousands of ghastly skeletons, sole rem- 
nants of its victims. This untrue statement 
was made by a Dutch traveller, named Foersch. 
It is undoubtedly true, that in Java there is a 
poisonous valley ; and it is also true, that in 
Java there grows a poisonous tree, called Upas, 
but so far from its creating desolation and 
death for the space of many miles, the Upas is 
a tree which grows in the most fertile situations, 
and is surrounded by the most luxurious vege- 
tation of an eastern clime. Twining plants 
creep round its stem — birds rest in its leafy 
branches — and beasts of prey come to sleep in 
its widely-spreading shade. 



150 UPAS, OR POISON-TREE. 

The poison-valley of Java has nothing to do 
with the Upas-tree at all. It is an excavation 
in the ground, about half-a-mile wide, and filled 
with carbonic-acid gas, just like the Grotto del 
Cane. 

Foersch, after assuring us that all he is going 
to say shall be perfectly true, gives a detailed 
account of the manner in which the Upas poi- 
son is obtained : he tells us that criminals under 
sentence of death are permitted to choose 
whether they will suffer by the public execu- 
tioner, or try their fortune in procuring some 
poison from the Upas. Of two evils they usu- 
ally prefer the latter, as it affords them a slight 
chance of escaping. If fortunate enough to 
return with some poison, then all their crimes 
are forgiven, and they, moreover, obtain a re- 
ward. 

" On the confines of the valley," says he, 
" there lives an old priest, whose duty it is to 
afford assistance, both spiritual and temporal, 
to such malefactors as are about to proceed on 
their generally fatal errand. At stated periods 
of the year bands of prisoners arrive at this old 
man's residence, and are there supplied with 
every requisite for performing their journey. 
The priest covers their heads with leather hoods, 



UPAS, OR POISON-TitEE. 151 

each having two glass eyes; supplies theui with 
a silver or ivory poison-box ; and then, ascend- 
ing with them the summit of a hill, he gives direc- 
tions for shaping their course, and, after com- 
mending their souls to the Almighty, he bids 
them farewell. They are directed to travel with 
the greatest speed, following the course of a 
little stream, which, atthedistance of thirty miles 
from this point, flows close past the tree. If the 
wind at the commencement of their journey 
should blow in the direction of the Upas until 
the first thirty miles are travelled over, then 
they are usualty safe ; but if the wind should 
blow in their faces and waft towards them the 
deadly poison, they surely die." 

Foersch afterwards proceeds to give a long 
account of an execution which he witnessed of 
fourteen of the emperor's wives, who were 
killed at one time by means of lancets poisoned 
with the juice of the Upas ! He attributes the 
general unhealthiness of Java to the presence 
of this solitary tree, which not only kills by its 
poisonous emanations, but also affords every 
facility to secret murder, almost all the natives 
of quality carrying poisoned daggers or knives. 
He affirms that the Dutch inhabitants of Java 
never travel into any distant part of the island 



152 UPAS, OR POISON-TREE. 

without taking with them fish, which they 
throw into water before presuming to drink it. 
If the fish live, all is well ; if they die, the water 
has been poisoned. Finally, he relates an anec- 
dote which, according to him, is current in Java, 
relative to the origin of the tree. It is repre- 
sented that at one time the inhabitants of that 
part of the island, which is now desolate, were 
very sinful, and the prophet Mahomet caused 
the Upas to shoot up as a scourge to destroy 
them all. 

One can hardly regret this fabulous account 
of the Upas-tree, seeing that it called forth a 
beautiful effusion from the late Dr. Darwin, 
who, in his poem called The Botanic Garden, 
or Loves of the Plants, thus describes it : — 

" Where seas of gold with gay reflection smile, 
Round the green coasts of Java's palmy isle, 
A spacious plain extends its upland scene, 
Rocks rise on rocks, and fountains gush between ; 
Soft zephyrs blow ; eternal summers reign, 
And showers prolific bless the soil in vain. 
No spicy nutmeg scents the vernal gales, 
Nor towering plantain shades the mid-day vales. 
No grassy mantle hides the sable hills, 
No flowering chaplet crowns the trickling rills, 
Nor tufted moss nor leathery lichen creeps 
In russet tapestry o'er the crumbling steeps. 
No step retreating on the sand impressed, 
Invites the visit of a second guest. 



CARBONIC ACID IN WELLS. 153 

No refluent fin the unpeopled stream divides, 
No revolant pinion cleaves the airy tides; 
Nor handed moles, nor beaked worms return 
That mining pass the irremeable bourne. 
Fierce in dread silence on the blasted heath 
Fell Upas sits — the hydra tree of death. 
Lo ! from one root the envenomed soil below 
A thousand vegetative serpents grow. 
In shining rays the scaly monster spreads 
O'er ten square leagues his far diverging heads, 
Or in the trunk entwists his tangled form, 
Looks o'er the clouds, and hisses in the storm. 
Steeped in fell poison as his sharp teeth part, 
A thousand tongues in quick vibration dart. 
Snatch the proud eagle towering o'er the heath, 
Or pounce the lion as he stalks beneath, 
Or strew as marshalled hosts contend in vain 
With human skeletons the whitened plain. 
Chained at his root, two scion demons dwell, 
Breathe the faint hiss or try the shriller yell, 
Rise fluttering in the air on callow wings, 
And aim at insect prey their little stings. 

Carbonic acid is very often found in wells, 
and would kill any person who might be rash 
enough to descend. This is a case in which 
you may with advantage exercise your chemical 
information. Carbonic acid, like nitrogen, does 
not support combustion ; therefore it is prudent, 
before descending a pit or well, to lower down 
a lighted candle ; if the flame should be extin- 
guished, you would kuow for certain that the 
descent was dangerous : but I will tell you how 



154 CARBONIC ACID — HOW PREPARED. 

to purify such a pit, so that a person may de- 
scend with perfect safety. Sprinkle some lime 
with water, and then let it be thrown down 
into the pit, after which you will find that the 
candle when lowered is no longer extinguished, 
because the lime has combined with the car- 
bonic acid, and has become converted into a 
substance called carbonate of lime. 

This remark brings me to the process for 
making carbonic acid : but you may say I have 
told you how to make it already — by the breath- 
ing of animals, by the burning of charcoal, and 
by the fermentation of beer : true, it may be 
made in those ways; but I am going to tell you 
a convenient process for making it ; a process 
which yields it in the greatest abundance, and 
of the greatest purity. 

I take a wine-bottle, furnished with a cork 
and bent tube ; indeed the same apparatus as I 
used for the preparation of hydrogen. I now 
put into the bottle some white marble, broken 
into small pieces, (chalk would have done,) 
and pour upon it a mixture of oil-of-vitriol 
(called sulphuric acid) and water. I now re- 
place the cork; wait till the first portions of 
gas have escaped, and then collect the remain- 
der in the usual manner. While a bottle is 



CARBONIC ACID HOW PREPARED. 155 

filling, I will explain to you the theory of the 
decomposition : marble and chalk are both car- 
bonate of lime ; that is to say, they are com- 
posed of lime and carbonic acid united to- 
gether. Sulphuric acid, on being added, takes 
away the lime, forming sulphate of lime, and 
carbonic acid escapes. The same decomposi- 
tion is thus expressed by means of a diagram: — 

Carbonate of C Carbonic Acid (escapes.) 

Lime (Chalk.) \ Um 



Sulphuric Acid _^Sulphate of Lime. 

The method which I have followed is the 
best for collecting carbonic acid ; but if you 
do not want it exceedingly pure another plan 
may be followed, depending for its success on 
the fact, that carbonic acid is much heavier 
than atmospheric air. I shall not go through 
the process, but describe it to you by means of 
a sketch. You may as- 
certain when the bottle 
is full of gas, by dipping 
into it a piece of lighted 
wood, the fire of which 
will be extinguished im- 
mediately that it touches 
the gas. 

We have now obtained 





156 CARBONIC ACID — PROPERTIES OF. 

several bottles full of carbonic-acid gas, and 
will perform a few experiments with it. I take 
a pint wide-mouthed bottle, and place it without 
its stopper on the table : then taking a bent 
wire, supplied with a lighted taper, I 
fix it thus. Now I take a bottle filled 
with carbonic-acid gas, and pour it, 
just as I would a liquid, upon the 
lighted taper, the flame of which is 
immediately extinguished. This ex- 
perimenthas somewhat the appearanceof magic, 
and would pass very well for a conjuring trick. 
It teaches us two things, that carbonic acid is 
much heavier than atmospheric air, and that it 
does not support combustion. 

Into another bottle containing this gas, I 
pour some lime-water ; which, having covered 
the mouth of the bottle with my hand, I shake 
briskly — see how white the lime-water has he- 
come. Lime-water, then, is a test for carbonic 
acid ; that is to say, will discover it : one sub- 
stance which is used for the purpose of dis- 
covering another is called by chemists a test. 
The white appearance is caused by the forma- 
tion of chalk, or carbonate of lime. So it appears 
that carbonic-acid gas, in many of its properties, 
resembles nitrogen. Carbonic acid, however, 
whitens lime-water, which nitrogen does not. 



CARBONIC ACID LIQUIFIED AND SOLIDIFIED. 157 

Carbonic acid must exist as a solid in mar- 
ble, chalk, limestone, and many other sub- 
stances, although we usually obtain it in the 
form of gas : however, this gas, by the applica- 
tion of immense pressure, may be converted 
into a liquid, and this liquid has lately been 
frozen into a solid, but the process requires 
some costly apparatus, and is highly dangerous. 

I have now said all that I consider to be ne- 
cessary about carbonic acid, and in our next 
Lecture we will discuss the compounds of oxy- 
gen and sulphur. 



158 



LECTURE XIV. 



COMPOUNDS OF OXYGEN WITH SULPHUR. HYPO- 
SULPHUROUS ACID; SULPHUROUS ACID; HYPO- 
SULPHURIC ACID ; SULPHURIC ACID. COM- 
POUNDS OF OXYGEN WITH SELENIUM PHOS- 
PHORUS BORON AND SILICON. 

The compositions of oxygen and sulphur unite 
in four different proportions to form four dif- 
ferent compounds, which is represented by this 
diagram. 



Hypo-sulphurous Acid 
Sulphurous Acid 
Hypo-sulphuric Acid 
Sulphuric Acid 


Parts by Weight. 


Atoms. 


Oxygen. 


Sulphur. 

16 
16 
32 

16 


1 Oxygen. 


Sulphur" 


8 
16 
40 

24 


i 

2 
5 
3 


1 
1 

o 

1 



Of these I shall only mention the second 
and fourth. Most persons have noticed the 
disagreeable smell which is produced by a 
burning match ; this depends upon the forma- 
tion of sulphurous acid, which is evolved in the 
gaseous state ; the process of combustion ef- 



SULPHUROUS ACID. 159 

fecting a combination between sulphur and 
atmospheric oxygen in the proportions neces- 
sary to generate this acid. 

It is a bleaching agent, as I can show you 
by a very simple experiment. Here is a red 
rose moistened with water, and at a little dis- 
tance underneath it I hold a burning brimstone 
match. The red leaves of the rose very soon 
lose their colour, and change to white. It is 
by a process not very different to this that 
ladies' straw -bonnets are bleached, which, if it 
were not for this treatment, would be very far 
from white. Although sulphurous acid may 
be procured as I have described, yet when re- 
quired in a pure condition another method must 
be followed. 

Take a small glass retort ; put into it some 
pieces of copper, or a little mercury, and then 
throw in enough strong oil-of-vitriol to cover 
the metal : afterwards apply the flame of a 
spirit-lamp, and sulphurous-acid gas comes 
over. By distilled water it is absorbed rapidly, 
but not by common water to an extent sufficient 
to prevent its being collected over a pneumatic- 
trough. Sulphurous acid neither burns nor is 
a supporter of combustion, as may be seen by 
lowering a bghted taper into a bottle full of it. 



160 SULPHURIC ACID. 

C I Sulphur ..Sulphurous Acid, (txcapea.) 

1 Sulphuric Acid ■ 2 Oxygen 

*- 1 Oxygen 

1 Copper _\1 Oxide of Copper 

1 Sulphuric acid, . _\ Sulphate of Oxide of 

Copper. 

I shall now speak of sulphuric acid, or oil-of- 
vitriol, which is a much more important com- 
pound. It is made by burning together a mix- 
ture of nitre (nitrate of potash) and sulphur, in 
such a manner that the results of combustion 
may be conveyed into a leaden chamber con- 
taining water. The exact nature of the changes 
which take place I shall not attempt to describe, 
knowing them to be too difficult for the com- 
prehension of such young chemists as those 
around me. I may tell you, however, that by 
this process every sixteen parts by weight, or 
one atom of sulphur, is made to unite with 
twenty-four parts by weight, or three atoms of 
oxygen. Sulphuric acid in its pure state is a 
while crystalline body r ; but the sulphuric acid, 
or oil-of-vitriol of commerce, is a chemical com- 
pound of pure sulphuric acid and water. Un- 
conibined sulphuric acid is usually an artificial 
compound, but it sometimes exists in the neigh- 
bourhood of volcanoes. Combined with other 
substances it is found in nature very largely : 



SULPHURIC ACID — TEST FOE. 161 

Epsom salt is composed of sulphuric acid and 
magnesia, it is therefore called sulphate of mag- 
nesia. Glauber's salt is sulphate of soda ; and 
plaster of Paris is sulphate of lime. Sulphuric 
acid powerfully reddens litmus-paper, and, 
whether alone or in combination, may be dis- 
covered by a very satisfactory test. Here is a 
wine-glass, containing some distilled water 
mixed with only one drop of oil-of-vitriol. I 
now pour in a little hydrochlorate of baryta : 
and, see ! what a copious white precipitate 
immediately falls. Any other soluble prepara- 
tion of baryta will do as well as the hydrochlo- 
rate. Many other white compounds are formed 
by solutions containing baryta, but none which 
possess the insolubility of sulphate of baryta : 
it may be collected and boiled in nitric acid 
without dissolving in the least degree, whereas 
all other white compounds formed by baryta 
are more or less soluble in nitric acid. 

The changes which take place on adding 
hydrochlorate of baryta to sulphuric acid, are 
these. Sulphate of baryta is formed, and hy- 
drochloric acid is set free. 

I now vary the experiment a little, and add 
hydrochlorate of baryta, not to sulphuric acid, 
but to a substance containing it — Epsom salt ; 

M 



102 COMPOUNDS OF OXYGEN. 

still, you observe, the same white compound is 
thrown down. 

The changes here are somewhat different. 
Sulphate of baryta is generated as in the former 
instance, but the hydrochloric acid is no sooner 
liberated than it unites with magnesia, forming 
hydrochlorate of magnesia. 

Oxygen combines with selenium, and forms 
acids which are very similar to those of oxygen 
and sulphur, but they are comparatively little 
known. 

Oxygen also unites with phosphorus in seve- 
ral proportions, to form different compounds, 
the principal of which is phosphoric acid. It 
never exists naturally, but when in combina- 
tion with lime, forming phosphate of lime, it 
enters largely into the composition of the bones 
of animals. 

Oxygen combines with boron in one propor- 
tion to form boracic acid. It never occurs as a 
natural product, but is obtained from borax, 
which is a borate of soda, or, to speak more 
correctly, a Jiborate of soda ; because there 
are two atoms of boracic acid combined with 
one of soda : bis or bi meaning twice. 

Oxygen and silicon combine in one propor- 
tion, only forming silicic acid or silica. Under 



MEANING OF THE TERM, BASE. 163 

the less ostentatious name of flints, all of you 
have many times seen silicic acid. 

I have already told you that flints are made 
up of an acid called silicic acid : true, it is not 
sour, nor does it redden litmus-paper, there- 
fore two principal characteristics of an acid are 
absent ; but it combines with bases and forms 
silicates, therefore chemists say that it is an 
acid. 

I have not yet told you what a base is ; you 
will best understand the meaning of the term 
by an example, which you shall have. Sul- 
phuric acid combines with soda and forms sul- 
phate of soda ; with magnesia, and forms sul- 
phate of magnesia; also with various other 
substances, each of which is called a base, and 
the combinations of acids with bases are termed 
salts. Just in the same manner silicic acid 
unites with soda, magnesia, and other sub- 
stances to form silicates. Glass is a silicate 
of soda, and, chemically speaking, is a salt. 

Do not mistake what I say ; there are salts 
without any acid at all, of which class com- 
mon sea-salt is an example, being composed of 
chlorine and the metal sodium ; still the greatest 
number of salts are formed by the union of an 
acid with a base. 

m 2 



164 



LECTURE XV. 

COMPOUND OF NITROGEN WITH HYDROGEN — 

(AMMONIA) — WITH CHLORINE IODINE — 

CARBON. 

Nitrogen and hydrogen combine together, and 
form the substance called ammonia. Now, I 
dare say, my young friends are tolerably fami- 
liar with some of the properties of ammonia. 
They have doubtless seen and smelt the 
liquid called hartshorn. Ammonia is a colour- 
less invisible gas, having a very strong odour; 
and hartshorn is nothing but a solution of am- 
monia in water. 

Whenever animal substances are burned or 
exposed to a great heat, ammonia is generated: 
formerly the shavings of hartshorn were alone 
employed, and hence a solution of ammonia 
obtained that name : but ammonia of great 
purity cannot be obtained directly from this 
source ; it is first necessary to make hydro- 



AMMONIA. 165 

chlorate of ammonia, and then to procure am- 
monia itself from this. 

In order to make ammonia, I proceed as fol- 
lows: — I take some lime, and sprinkle on it 
just enough water to make it crumble into 
powder. This powder is a compound of water 
and lime, called by chemists hydrate of lime. 
I now powder in a mortar some sal-ammoniac, 
(hydrochlorate, or muriate of ammonia,) which, 
by the way, is no very easy matter, and requires 
some little exertion. Having at length done 
it, I mix together in a mortar equal parts of 
this powdered sal-ammoniac and hydrate of 
lime ; which mixture I immediately put into a 
stoppered retort, through the tubular or stopper 
opening. I now replace the stopper, and hav- 
ing put the beak of the retort under mercury,* 
I apply the heat of a spirit-lamp, which causes 
ammoniacal gas to be evolved in abundance. 
The first portions I allow to escape, of course, 
and the remainder I collect. As it is desirable 
to obtain the gas as dry as possible, you will 
remark that in the neck of the retort I have 

* It is difficult to get mercury so very pure that it will 
not soil the interior of a collecting-jar, therefore for all ordi- 
nary experiments the process of displacement is infinitely 
preferable. 



Lime- 



166 AMMONIA — HOW COLLECTED. 

placed a roll of blotting-paper, which, of course, 
will absorb any moisture. 

( Ammonia (escapes.) 

Hydrochlorate J 
of Ammonia. ) Hydrochloric S Hydrogen 

( Acid. I Chlorine-^ \ 

C Oxygen \ \ Water. 

-) \ 

( Calcium _ \ Chloride ot 

Calcium. 

Ammonia has such strong affinity or desire, 
.so to speak, for water, that we cannot possibly 
collect it as we have other gases. Instead of 
water we must substitute the liquid metal 
quicksilver. In the shops are sold very strong 
pneumatic-troughs, generally made of cast-iron, 
and intended to contain mercury instead of 
water, for the purpose of collecting those gases 
which water would absorb. 

Now we will employ, instead of mercurial - 
troughs, finger-glasses, and collect our gas in lit- 
tle bottles. Ammonia maybe procured, however, 
tolerably pure without the aid of any mercury 
at all, by the process of displacement. This 
process I mentioned when speaking of carbonic 
acid ; but ammonia is a much lighter gas than 
the atmosphere, therefore it cannot well be col- 
lected downwards like carbonic-acid, but up- 
wards ; thus : — 



AMMONIA TEST FOR. 



167 




We have now several bottles which have 
been filled with ammoniacal gas by means of 
mercury ; but they are so exceedingly small, 
that for the purposes of illustration I shall col- 
lect some fresh gas, by the less perfect, but 
more convenient process of displacement. Hav- 
ing arranged the apparatus, as represented by 
the diagram, I now commence the operation. 
The gas is invisible, therefore I cannot see 
when it overflows the bottle, yet I can smell it; 
or I can have recourse to a still more delicate 
and much prettier test. 

I hold near its mouth a glass rod, which has 
been dipped in spirit of salt, (hydrochloric or 
muriatic acid,) and immediately the gas over- 
flows, it unites with the acid, and causes white 
fumes, which are composed of little particles 
of sal-ammoniac. Here is an instance, then, of 
two invisible bodies uniting to form a solid ; 



1 68 ALKALIES TEST FOR. 

for the vapour of hydrochloric acid and ammo- 
niacal gas, are both of them invisible. 

I now invert a bottle full of ammoniacal gas 
under water and shake it well ; having pre- 
viously removed the glass plate, see how the 
water rushes up and entirely fills the bottle. 
This experiment teaches us what a very great 
affinity, or desire to unite, ammonia and water 
evince for each other. We shall find, on ex- 
amining this solution, that it has all the pro- 
perties of hartshorn. 

Into another bottle filled with this, I throw a 
bit of turmeric-paper, previously moistened 
with distilled water ; and remark how very 
brown the paper becomes. This is a very im- 
portant experiment : ammonia belongs to the 
class of substances termed alkalies, and all al- 
kalies render turmeric-paper brown. 

In a previous experiment I have already 
shown you that acids change the blue colour of 
litmus-paper to red. I now throw a bit of red- 
dened litmus-paper into a bottle full of ammo- 
niacal gas, and the original blue colour is im- 
mediately restored. 

We shall require ammoniacal gas for a future 
experiment, therefore let us place a bottle full 
of it aside. 



POISONED PICKLES. 169 

If I drop a little hartshorn, or solution of am- 
monia in water, into a solution of a salt of cop- 
per, the mixture immediately acquires a deep 
blue tinge ; in this manner we may detect the 
presence of copper in pickles, which are fre- 
quently adulterated with it in order that they 
may preserve a green colour. How foolish to 
mix a slow poison with an article of food merely 
for the sake of imparting an agreeable colour ! 

With chlorine and iodine, nitrogen forms two 
most dangerous compounds ; the slightest touch 
causes a violent explosion : once made, they 
cannot be handled, and a person is never safe 
when they are near. Monsieur Ampere, the 
discoverer of chloride of nitrogen, lost an eye 
and a hand in prosecuting his experiments on 
it ; and two accidents by the same substance 
have come within my own personal observation. 
Under these circumstances I shall not teach 
you how to make either the chloride of nitrogen 
or the chloride of iodine. 

Carbon and nitrogen unite to form a sub- 
stance called cyanogen, from the Greek word 
kuanos, blue ; because it enters into the com- 
position of Prussian blue, which is composed of 
cyanogen and iron. 

Cyanogen is also called the bicarburet of ni- 



170 HYDROCYANIC, OR PRUSSIC ACID. 

trogen, because its composition is two atoms of 
carbon and one of nitrogen. Cyanogen, when 
united to hydrogen forms that most deadly poi- 
son, named hydrocyanic, — or, because it is made 
from Prussian blue, Prussic acid. 



171 



LECTURE XVI. 

COMPOUNDS OF HYDROGEN WITH CHLORINE — 

IODINE BROMINE FLUORINE CARBON 

SULrHUR SELENIUM — PHOSPHORUS. 

I shall now describe a very important com- 
pound : hydrochloric, or muriatic acid, a solu- 
tion of which in water is commonly termed 
spirit of salt. Hydrochloric acid, as its name 
indicates, is a compound of hydrogen with 
chlorine, and in its natural state is a gas, some 
of which I presently intend making. 

Hydrochloric-acid gas, like ammonia, cannot 
be collected over water ; we must either employ 
a mercurial trough, or else have recourse to the 
process of displacement. The bottles used for 
collecting the gas in question should be perfectly 
dry : see with what scrupulous care I attend to 
this point: my bottles have been standing before 
the fire until they are quite warm, and now I wipe 
them out with a silk handkerchief, which, as 



172 HOW TO DRY A BOTTLE. 

they are large, I find no difficulty in doing, but 
I dare say it would puzzle you to dry a small- 
necked bottle, except you were shown the 
way. 

Drying means the dissipation of a liquid in 
the form of steam, which dissipation cannot 
take place except there be a current, or draft : 
and in a bottle or other vessel possessing but 
one opening there cannot be a very powerful 
current. How, then, would you dry a small- 
necked bottle ? I will tell you. 





i 






■ 


■ : 




/ 


till"?! \ 




y£ •< 


1>~ •'■"•*■' 


•::- \ \ 




1 


flu "^M 






Mggj 




r r . 



Having made it warm, insert a tube like this 
and suck out air from the bottle several times, 
by which means the moisture is also sucked 
out, and the bottle is dried. If this moisture 
be injurious of course you would take care that 
it might not get to your lungs, but you would 
perform suction by means of the mouth alone. 

Not only have I dried the bottles, but I have 



HYDROCHLORIC, OR MURIATIC ACID. 173 

likewise placed a roll of dry blotting paper into 
the neck of the retort, for the purpose of ab- 
sorbing all moisture. It may be collected in 
the greatest purity by means of the mercurial 
trough ; but although the process is very cor- 
rect, yet it soils the bottles, and I shall there- 
fore resort to displacement in preference. Into 
the beak of the retort I insert a bent tube, by 
means of a cork. Now, all matters being 
arranged, I pour upon the salt enough strong 
oil-of-vitriol to cover it : then I apply the heat 
of a spirit-lamp, and collect the gas which 
comes over. 

i 1 Chlorine — -y 1 Hydrochloric Acid- 

1 Chloride of Sodium < _.x Gas ( stupes. I 

t 1 Sodium 



Jl Hydrogen 
(. 1 Oxygen 

1 Sulphuric Acid 



There is no difficulty in ascertaining when a 
bottle is filled, because the gas no sooner flows 
over, and comes into contact with atmospheric 
moisture than it forms dense white fumes. On 
observing this, I immediately close the bottle, 
by means of its own stopper, or a greased glass 
plate. Into one of our bottles I drop a slip of 
litmus-paper, and it immediately turns red ; the 




174 HYDROCHLORIC ACID TESTS FOR. 

result of this experiment demonstrates that the 
gas possesses acid properties. 

Into another bottle I immerse a lighted taper, 
which is immediately extinguished, and the 
gas does not inflame. We learn, then, that it is 
neither a supporter of combustion nor a com- 
bustible. 

Another bottle full of the gas I invert un- 
der water, when, on removing the stopper, the 
liquid rushes up with a violence almost amount- 
ing to an explosion : the bottle now contains a 
solution of the gas in water, which you observe 
reddens litmus-paper, like the gas itself, and is 
moreover sour to the taste. It is, in fact, weak 
spirit of salt. 

The next experiment I shall show you will 
be very striking indeed. You remember my 
using a glass rod dipped into spirits-of-salt, as 
a test for ammonia, with which it produced 
white fumes : I will now show you those 
fumes in a more striking manner. In one hand 
I hold a bottle full of ammoniacal gas, and in 
the other hand a bottle full of hydrochloric- 
acid gas, both of which are covered by glass 
plates. I bring the mouths of the bottles to- 
gether, and will trouble one of you to pull 
away the two plates. 



HYDROCHLORIC ACID TESTS FOR. 175 



Now see the fumes, the whole room appears 
full of smoke : this, indeed, is a conjuring 
trick. I bring two apparently empty bottles 
together, and their mere approach fills the 
whole room with smoke. The explanation of 
the mystery is this : hydrochloric acid gas is 
invisible, ammoniacal gas is invisible, but a 
combination of the two, hydrochlorate of am- 
monia, is a dense white solid. As nitrate of 
the oxide of silver is a test for chlorine in the 
uncombined state, so is it a test for all soluble 
compounds which contain chlorine ; therefore 
on adding a solution of nitrate of oxide of sil- 
ver to hydrochloric acid, either in a gaseous 
state or dissolved in water, a white curdy sub- 
stance falls, which is soluble in ammonia and 
insoluble in hot nitric acid, proving that it is 
really the chloride of silver. 

With iodine and with bromine hydrogen 



176 HYDROFLUORIC ACID — HOW PREPARED. 

combines, and forms hydriodic and hydrobro- 
mic acids ; with fluorine it forms hydrofluoric 
acid, which has the curious property of dissolv- 
ing glass. 

I take a piece of window-glass, and having 
made it warm I smear it with bees-wax ; now, by 
means of a needle I scrape away the wax in va- 
rious parts, and sprinkle the glass thus pre- 
pared with a little fluor-spar, on which I throw 
some strong oil-of-vitriol. Violent chemical ac- 
tion immediately takes place, on account of the 
production of hydrofluoric acid, which corrodes 
the glass, and renders it dull wherever the wax 
has been scraped away from its surface : in 
this way may be prepared very beautiful draw- 
ings. Now about the theory of the process: 
fluor-spar is composed of fluorine united to a 
metal named calcium, and is therefore called 
fluoride of calcium. Oil-of-vitriol is composed 
of sulphuric acid and water; a diagram will 
best explain the rest. 

1 Fluoride *i 1- * luorine ..._. 1. Hydro-fluoricAcid(e»caf>«.) 
of Calcium. 5 liCaldum 



1. Water- 



' 1 . Hydrogen _.\ 

. 1. Oxygen A Lime. 



I. Sulphuric Acid ]. Sulphate of Lime. 



FIRE-DAMP. 177 

Hydrogen and carbon unite in a great many 
proportions, some of which are very curious 
and unusual. 

Coal gas, now so much burned for the pur- 
pose of illumination, is a mixture of a great 
many different compounds of carbon and hy- 
drogen. It is chiefly made up, however, of 
wiorto-carburet of hydrogen, a gas consisting 
of one atom of carbon and one of hydro- 
gen. Mono-carburet of hydrogen cannot be 
made artificially, but it is evolved from stag- 
nant water and the mud of ditches. Coal- 
mines sometimes furnish it in prodigious quan- 
tities, and when mixed with atmospheric air, it 
constitutes the terrific fire-damp so fatal to 
coal-miners. You remember my showing you 
thatamixture of hydrogen andatmospheric air is 
explosive; well, a mixture of carburetted hydro- 
gen and atmospheric air is also explosive. Some- 
times coal-mines are filled with this mixture, and 
you may form some idea of the consequences 
which result if it be set on fire. The dreary laba- 
rynths of the mine are filled with raging flames, 
accompanied by a sound like thunder; and the 
poor workmen are either shot into the air, as 
from a piece of artillery ; or maimed, scorched, 
and bleeding, they only escape this calamity to 




178 CHOKE-DAMP. 

be suffocated by the noxious gases which fill 
the mine after the explosion : these are called the 
choke-damp, the nature of which I can best 
describe to you by means of a diagram. 

!r Xitr °e en ) Choke- 
Atmospheric J 0xy gen Carbonic Acid J dam P' 
lOxygen^ 
Carburetted (Carbon/ 
' ° t Hydrogen j Water. 

From an inspection of which it appears that 
the results from the explosion of fire-damp are 
water and two most poisonous gases — nitrogen 
and carbonic acid ! 

When sitting around your cheerful fires you 
little think amidst what dangers the fuel has 
been sought : you little think of the life which 
the poor miner leads. For the sake of a trifling 
pittance he shuts himself out from the light of 
heaven, and spends his days in the gloomy re- 
cesses of a coal-mine, where the fire-damp, 
brooding like a shadow of death, may in one 
minute launch him into eternity. 

It was for the purpose of obviating those 
dangers in some degree, that the celebrated 
chemist, Sir Humphry Davy, constructed his 
safety lamp, the principle of which I will 



NATURE OF FLAME. 179 

describe to you ; but I must previously make 
you acquainted with the nature of flame. Flame 
is nothing more than burning gas ; but in order 
to burn, it must possess a certain degree of heat ; 
and if a sufficient portion of this heat be taken 
away, flame cannot exist. 

I can illustrate what I mean by a common 
candle or taper ; which, after all, is a gas-burner, 
but the gas is manufactured from the tallow 
immediately that it is required, whereas some 
gas-burners derive their supply from a gaso- 
meter. 

But to return to my subject : — that I may 
illustrate the nature of the safety-lamp. I 
bend a piece of thick iron or brass wire into 
this form, and holding the ring part over 
the flame of a candle, I gradually lower it until 
it surrounds the wick, and in this manner I 
extinguish the flame ; because the wire con- 
ducts or carries away heat with such rapidity 
as to cool the gaseous matter below the degree 
necessary for the existence of flame. 1 need 
scarcely inform you that the shape of the turn 
in the wire has nothing at all to do with its 
cooling effect, and that a square turn would 
answer as well as a round one. Now you are 
prepared to understand the construction of Sir 

n2 



180 



SAFETY-LAMP Ob" SIR H. DAVY, 




Humphry Davy's safety-lamp, which 
consists of a common lamp, sur- 
rounded with a cage of wire-gauze, 
every aperture through which has 
the same effect as our small iron 
ring. The fire-damp, then, may 
ignite inside the cage and fill it with 
flame, but this cannot -pass through, 
at least while the lamp is still, or 
the explosive mixture not moving 
in currents. 

The wire-gauze, it is true, may 
become red hot, yet even then it is 
much cooler than flame, and provided the lamp 
be kept still, and employed in atmospheres of 
fire-damp, which are also still, I believe no dan- 
ger can occur. But I am convinced that the 
lamp is not proof against currents of fire- 
dami), which may at first render the wire-gauze 
red-hot by directing flames against it, and then 
make the flames pass through. 

It is right for society to venerate distinguished 
men, and to award to them every praise which 
their merits may have earned ; but in some 
cases this feeling is carried to excess. Divines, 
warriors, statesmen, poets, and natural philoso- 
phers ; in short, all who stand out in high and 



NOT SAFE UNDER ALL CIRCUMSTANCES. 181 

bold relief from the general mass of society, at 
first experience difficulty in establishing a 
name ; but no sooner is this name acquired,— 
no sooner has an individual wreathed his brows 
with laurels of his own fame, than the over- 
anxious and unjust populace bedecks them with 
stolen gems, and as mankind will enrich the 
gentleman who begs for a wager, while an object 
of charity is allowed to starve, so will they swell 
the long list of honours already belonging to 
some distinguished man, by denying to a more 
humble individual a credit which is justly his due. 
We must not offer up truth as sacrifice to the 
memory of Davy : the shade of that truly great 
man would spurn the incense. His numerous 
masterly discoveries have conferred on him a 
fame which is imperishable; and his name, iden- 
tified as it is with some of the sublimest philo- 
sophical truths, can never be mentioned but with 
respect. Wrong, then, as injustice must be 
under every circumstance, it becomes doubly 
so when perpetrated without even the shadow 
of a cause. I am not apprehensive of diminish- 
ing the fame of Sir Humphry Davy, by show- 
ing that one of his discoveries has been applied 
to practice with greater success by a working 
miner than it was originally by himself; and 
even if 1 were, I ought, nevertheless, to be just, 



182 roberts's safety-lamp. 

and to state the undeniable fact, that there are 
circumstances under which the so-called safety- 
lamp of Sir Humphry Davy is not safe, and 
for reasons which I have already explained. 
The only safe modification of it that I am aware 
of was devised by a working miner, named 
Roberts, a person of great comprehension and 
natural abilities. 

He has invented a lamp which I believe to be 
safe, whether surrounded by fire-damp at rest or 
in motion; and I cannot possibly divine the rea- 
son why it is not employed in our large coal- 
mines except that the name of Mr. Roberts, a 
miner, has not the weight which is attached to 
the name of Sir Humphry Davy. Still we 
must remember that Mr. Roberts has merely 
added something to the original discovery of 
Davy, and that to the latter philosopher (for I 
call both philosophers) we are indebted for 
some masterly experiments, by which he de- 
termined that small metallic apertures were an 
impediment to the passage of flame ; a fact of 
the highest importance, for even the flame of 
the most explosive gas that exists, I mean a 
mixture of oxygen and hydrogen can be en- 
tirely arrested by means of several layers of 
wire-gauze.* 
* In the lamp of Sir H. Davy, the only safeguard against 



COAL GAS — HOW MADE. 183 

Gas, which is employed for the purposes of 
illumination, is either made from coal or from 
oil, and consists, as I before mentioned, of se- 
veral carburets of hydrogen mixed together. 

Coal gas is made by exposing coal to a red 
heat in large iron retorts, by which means there 
are generated several carburets of hydrogen, 
tar, and sulphuretted hydrogen, all mixed to- 
gether. The impure gas as it gets cold de- 
posits its tar, and afterwards is freed from sul- 
phuretted hydrogen by being passed through 
lime-water. It is now collected in immense 
vessels, called gasometers, and thence distri- 
buted in various directions through pipes. 

The process for making oil gas is slightly 
different. Fish-oil is caused to drop gradually 
on a piece of red-hot iron, and by this means 

an explosion is a single layer or envelope of wire-gauze; 
two layers, or even more, might be employed, it is true, but 
such an arrangement affords just as much impediment to 
light as to flame, and hence the instrument's utility is in 
great measure destroyed. The wick of Sir H. Davy's lamp 
obtains a supply of air from every part of the wire-gauze 
surrounding it, but Mr. Roberts causes the wick in his 
lamp to be supplied with air entirely from below, and this 
air can only arrive within the lamp by passing through 
many layers of wire-gauze. His lamp, then, may be de- 
scribed as a common safety-lamp, perforated in the bottom, 
screwed upon a brass box, which is filled with wire-gauze, 
and surrounded with a cylinder of glass. 



184 HYDROSULPHURIC ACID GAS 

it is immediately converted into gas, which 
passes into proper gasometers. 

Hydrogen and sulphur unite in two propor- 
tions, forming sulphuretted hydrogen, also called 
hydrosulphuric acid and persulphuretted hy- 
drogen. 

Sulphuretted hydrogen, or hydrosulphuric 
acid, is a gas which is plentifully evolved from 
the earth in volcanic regions, and in smaller 
quantities from decaying animal matters ; it 
also is a constituent of certain mineral waters. 
Sulphuretted hydrogen is a very disagreeable, 
but nevertheless a very useful gas. 

The importance of sulphuretted hydrogen 
induces me to show you how to prepare it ; but 
the process, if you please, shall be gone through 
in the open air. It is a most valuable test for 
metals, and for the purpose of illustrating this 
property, I must trouble you with its disagree- 
able smell. 

Now metals are not soluble in water. I 
might keep a sixpence immersed in water for 
any length of time without dissolving the least 
particle of it ; but if I add to the water a little 
nitric acid, then the silver will be dissolved. I 
shall speak of this more fully by and by ; all 
I wish you to recollect at present, is that me- 
tals can be dissolved. 



IS A TEST FOR METALS. 



185 



I have before me four different solutions con- 
taining four different metals, lead, arsenic, anti- 
mony, and zinc ; through these I will pass a 
current of hydrosulphuric acid gas ; but first 
let me make it. Into a Florence flask I put 
about half an ounce of a substance called sul- 
phuret of iron, and over this I pour a mixture 
of six parts of oil-of-vitriol and one of water. 

Now I fix into the mouth 
of the flask a cork fur- 
nished with a bent tube, 
through which the gas 
passes in abundance. First 
I dip the tube into the 
solution of lead, and see 
how black it turns. I now 
dip it into the solution of 
arsenic, which becoms yellow; into that of an- 
timony, and a red colour is produced ; into the 
zinc solution, and the colour is white. Now 
with many metals besides lead will this gas 
produce a black colour, but I could distinguish 
them one from another by various tests. I 
know, however, that there are only three me- 
tals which produce a yellow colour with the 
gas, and but one that yields a white ; while an- 
timony is the only metal that furnishes a red 




186 EFFECTS ON A LADY'S PAINTED FACE. 

colour. If I pass a stream of hydrosulphuric 
acid gas through water, a great deal is ab- 
sorbed, and there is obtained a solution which 
is very often advantageously employed as a test 
for metals instead of the gas itself. Hydro- 
sulphuric acid gas enters into the composition 
of certain mineral waters ; Harrowgate water, 
for instance, contains a large quantity of it ; 
and connected with this subject, I have an an- 
ecdote to relate to you. It was a practice 
with those ladies who were particularly ambi- 
tious of possessing a white skin, to daub them- 
selves with a preparation of the metal bismuth, 
which is one of these that sulphuretted hydro- 
gen blackens. Now it is represented on credit- 
able authority, that a lady made beautifully 
white by this preparation, took a bath in the 
Harrowgate waters, when her fair skin changed 
in an instant to the most jetty black. You 
may judge how much was her surprise at this 
unlooked-for change ; uttering a shriek, she is 
reported to have swooned ; and her attendants, 
on viewing the extraordinary change, almost 
swooned too, but their fears in some measure 
subsided on observing that the blackness of the 
skin could be removed by soap and water. The 
lady soon recovered from her trance, and de- 



ACTION ON METALLIC SOLUTIONS. 187 

rived some consolation from having the true 
state of things explained to her by her physi- 
cian, although she was not very well pleased 
that people should have discovered the philo- 
sophy of her white skin. 

If any ladies continue to use this prepara- 
tion, I would advise them to take particular 
care that they do not sit too near a coal fire, 
for their features would assuredly grow dark 
and dusky, from the action of sulphuretted 
hydrogen, which is produced by burning coal. 
Solutions of lead, then, are blackened by sulphu- 
retted hydrogen, and this metal enters into the 
composition of white paint ; hence we account 
for the dark colour of mantel-pieces which were 
originally painted white. 

The theory of the action of this gas when 
passed through metallic solutions, is very simple. 

Suppose we refer to the lead solution ; that 
which I used contained acetate of the oxide of 
lead. On passing through it a stream of hydro- 
sulphuric acid gas, the changes which ensued 
are represented by this diagram. 

C Acetic Acid feet free.) 

Acetate of Lead I 

i Oxide of Lead 



f Hydrogen ' 

Hydrosulphueic Acid < 

I Sulphur ^SulphuretofLeed. 




188 HYDROSULPHURIC ACID GAS COMBUSTIBLE. 

From which it appears that acetic acid is set 
free, water is formed, and black sulphuret of 
lead is thrown down, or, as chemists say, is 
precipitated. I have already remarked, that 
metals in an uncombined state are not soluble 
in water, they must be in combination. If we 
form a precipitate by passing hydrosulphuric 
acid through a metallic solution, this precipitate 
is a combination of the metal with sulphur, and 
is called a sulphuret. 

I shall now show you two more experiments 
with hydrosulphuric acid, and then close the 
subject. Into a bottle full of the gas I lower a 
lighted candle, which is immediately extin- 
guished, although the gas itself burns and de- 
posits sulphur. By this experiment I prove it 
to be a combustible, although not a supporter 
of combustion. 

I have here another bottle full of it, which 
corresponds in size to a bottle full of chlorine. 
Now I bring the mouths of them both together, 
and see what takes place — the two colourless 
gases react violently on each other, and sulphur 
is deposited. 

With this experiment I conclude my remarks 
on hydrosulphuric acid; a substance of so 
much importance that I could wish its smell 
were not quite so disagreeable. 



PHOSPHURETTED HYDROGEN. 189 

Hydrogen and selenium unite to form a gas 
which resembles in many of its properties hy- 
drosulphuric acid. Hydrogen and phosphorus 
unite in two proportions, forming two different 
gases : one called the /jrofo-phosphuret, and 
the other the /w-phosphuret of hydrogen. I 
shall only notice the latter, which can be made 
in various ways ; but it may be best prepared 
by throwing pieces of a substance termed phos- 
phuret of lime, into a mixture of water and 
hydrochloric acid, when phospuretted hydrogen 
gas is evolved in bubbles, and bursts into flame 
immediately on coming into contact with the 
air. The Will-o'-the-wisp, or Jack-o'-lantern, 
which is sometimes observed in the neighbour- 
hood of burying-grounds may probably be 
nothing but perphosphuretted hydrogen gas, 
evolved from the bodies underground. 



I must confess that notwithstanding all the 
eulogiums which were passed by our instructor 
upon the utility of sulphuretted hydrogen gas, 
its very disagreeable smell caused us to regard 
it with feelings of no great pleasure. It was 



190 A WALK PROPOSED. 

not to be expected that we could avoid breath- 
ing some of it, although we did our best endea- 
vours to prevent this, and every project that 
our ingenuity could devise was resorted to with- 
out effect : the gas would get down our throats, 
and so indeed it did. 

It was about five o'clock in the afternoon of 
a beautiful May day when the Lecture termi- 
nated. The birds sang merrily in the budding 
trees, and the sweet odour of the wild hedge- 
flowers afforded a pleasing contrast to the smells 
which we had been enduring. I do not know 
whether our Lecturer had been heard with less 
attention than usual, or whether he saw de- 
picted on our features any signs of disgust or 
dislike to the studies in which we had been 
engaged ; but I have reason to believe that we 
all looked very unamiable, and that such was 
observed to be the case by the good old man. 
Anxious as he always was to afford us rational 
amusement, and fearful lest our fondness for 
philosophy might suffer some diminution, his 
anxiety on this occasion was greater than I 
ever observed it before. Puffing and sneezing, 
holding our noses, and making wry faces, we 
were walking sullenly towards our homes, when 
our good-natured old friend, tapping us play- 



A TALE. 191 

fully on our heads with his walking-cane, pro- 
posed a walk in the fields, telling us that he 
would relate a funny tale about this sulphuret- 
ted hydrogen gas. The walk was agreed on, 
and the tale was told : I will relate it as near 
as possible in the old man's words. 



A TALE 

ABOUT A GIANT AND A DWARF. 

Of all the merry-makings which it has been 
my lot to see, none has ever pleased me so 
much as a village fair. The Lord Mayor of 
London's show, the King's visit to parliament, 
and all other fine sights put together, never 
afforded me half the gratification that I have 
felt from being present at a country fair. But 
my recollections of all country fairs are not 
pleasant, as will appear in the course of the 
tale which 1 shall presently relate ; although I 
am convinced that the chastisement which I 
then suffered for an act of wanton mischief 
taught me a useful lesson for my guidance in 
after life. It taught me in a practical manner 
something which I had heard theoretically 
advanced many times before : that knowledge 



192 PREPARATIONS FOR A FAIR. 

is power, either for good or for evil, and is only 
conducive to happiness when enlisted on the 
side of virtue. 

In the early part of June, some sixty years 
ago, I was present at the annual fair of my vil- 
lage. I was then about ten years old. The 
approach of the fair-day was a subject of plea- 
surable anticipation for every one within a 
dozen miles of the place : the village cottages 
were whitewashed ; the rose-tress were pruned; 
the garden-walks were nicely weeded, and 
brushed clean from leaves ; the cottage-doors 
were painted ; and, in short, every thing was 
done that could make our homes more com- 
fortable or more neat ; for the fair-day was one 
of hospitality to all strangers ; and to have re- 
ceived them in negligence or untidiness would 
have seemed to us the height of ill-breeding. It 
was a pleasing sight for us boys, when perched 
upon the cottage-roofs, or seated on the bough 
of some tall tree, to watch the busy prepara- 
tions which were making for the approaching 
festivities. Some were employed in partition- 
ing off the village-green into square divisions 
for the cattle : some were erecting booths for 
sweetmeats and toys, and some were fixing 
swings and round-abouts ; while in another 



PREPARATIONS FOR THE FAIR. J 93 

part of the green the village authorities were 
in earnest conversation with mountebanks, 
showmen, conjurers, and fruit-sellers, respect- 
ing the price which each should pay for a cer- 
tain space of ground. No statesmen, settling 
a treaty between nations — no warriors, inspect- 
ing the field of an approaching battle, could 
look more serious and sedate than these : if 
their very lives had depended on the termina- 
tion of the conference they could not have 
looked more grave. The heads of some were 
moving from side to side ; the heads of others 
were moving up and down; some grasped their 
pockets convulsively, and turned on their heels ; 
some curled their lips and counted their fin- 
gers : in short, a careful observer, placed far 
enough away to be out of hearing, but still 
within sight, might have seen depicted in their 
ever-changing gestures, all those varieties of 
feeling which are manifested in the course of 
mercantile transactions of the most extensive 
kind. 

Far beyond this busy scene the horizon was 
clouded with rising dust, caused by the ap- 
proaching cattle and caravans. In a short time 
they were distinctly visible, and in the space of 
a few minutes more we saw them descend the 

o 



194 PREPARATIONS FOR THE FAIR. 

hill immediately opposite to their place of des- 
tination. The cattle galloped and frolicked as 
if they too enjoyed the approaching festivi- 
ties ; and so perhaps they did, for none of 
them were tired from long travelling, having 
merely come from adjoining farmsj and if 
they could be pleased with their own fine 
appearance, and experience a little of human 
vanity in being gazed on and admired, they 
must have felt pleasure indeed : be this so or 
not, they did appear pleased ; why I cannot 
tell. Now came donkies, with gingerbread, 
fruits, and toys ; carts, with mountebank-stages, 
balancing-poles, swings, and round-abouts ; 
then followed caravans with wild beasts, 
penny-peeps, giants, and dwarfs ; next the 
more humble punchinellos, dog-cart men, and 
blind fiddlers ; who, having allowed the aris- 
tocracy of the craft to advance before, now fol- 
lowed in the rear. The bells all the time con- 
tinued ringing merrily, and thus passed away 
the evening. 

Now I must suppose the night spent ; not in 
sleep, at least, by me, for 1 was too anxious ; 
however it was spent, and the fair-day had 
arrived, which brings me to the subject of my 
tale. I am sorry to own that when young I 



AN ADVENTURE. 195 

employed my little stock of scientific know- 
ledge chiefly in playing practical jokes, and 
this propensity did not entirely leave me 
until the fair-day, which I am now about 
to describe. Scarcely waiting to finish my 
breakfast, I sallied out with some of my 
young friends in search of adventures, and 
passing along a row of show-caravans, I was 
struck with the appearance of a picture, re- 
presenting a giant and a dwarf, who were to be 
seen inside, together with a boa-constrictor 
and an alligator, all for the sum of one penny. 
Attracted by the harmony of a kettle-drum and 
cracked trumpet, a larger crowd of spectators 
surrounded this caravan than any other ; and 
the managers were enjoying in consequence an 
undue monopoly. The wild beasts' men in 
vain bawled forth the names and nations of 
their wonderful animals. Punchinello jab- 
bered to the empty air, and the mountebanks 
danced and grimaced in vain; the giant, dwarf, 
alligator, and boa-constrictor were all the rage; 
and the trumpet and kettle-drum drew wonder- 
ing crowds into the caravan. " I have sartinly 
seed many a bigger fellow than he," said a 
countryman, stepping out. " If I beant mis- 
taken," continued another, " the feller is on 



196 A MISCHIEVOUS TRICK. 

stilts, and if a body could make un come out 
upon the ground and show his inches fair and 
undeceitfully, he would look a wonderful dif- 
ferent man." 1 do not know how it was, but 
this conversation aroused in me the most plea- 
surable sensations : I reasoned myself into a be- 
lief, that if there was any deceit in the matter, 
T should act properly in exposing it, by ex- 
hibiting the giant in his full proportions. When 
the mind is bent upon the performance of 
some mischievous trick, we first quiet con- 
science by endeavouring to clothe our evil pro- 
pensities in a garb of virtue; — so was it with me; 
I fancied that by drawing the giant out I 
should exhibit any deceit that there might be ; 
and if there should be no deceit, then the giant 
might walk in again. But my conscience was 
not quite satisfied upon this point, inasmuch as 
the dwarf too must certainly experience some 
inconvenience if my proposed measure should 
be carried into execution : — perhaps also the 
alligator and snake might suffer. However, I 
had determined that the giant should come out, 
and conscience in vain whispered — no. 

Returning home, I selected a basin, provided 
myself with ingredients for making this dis- 
gusting sulphuretted hydrogen, and filling the 



AN ENRAGED GIANT. 197 

basin with nuts, the better to disguise my 
schemes, I crept stealthily under the giant's 
caravan, where, having set on the preparation 
of my gas, I retreated as fast as I could, allow- 
ing the noxious stench to ascend through the 
cracked and separated flooring of the caravan. 
Standing at a little distance on a hillock, I 
watched the result. " Walk in, ladies and gen- 
tlemen" bawled the conductor; " squeak" went 
the trumpet, " bang" went the kettle-drum ; 
but all in vain, the ladies and gentlemen kept 
walking out instead of walking in ; their faces 
contorted and their noses compressed. Pre- 
sently the musicians too left their posts, for the 
stench was intolerable. Another moment, and 
the ground was cleared for the space of many 
yards around the caravan ; that is to say, all 
had left it but myself, who, standing on the 
little hillock, was enjoying a sight of the mis- 
chief which I had created. Whilst I was one 
of the crowd, my ecstacies, for aught I know, 
might have remained unnoticed ; but standing 
alone they must necessarily have been re- 
marked, and, indeed, so they were. Presently 
the dwarf gave a convulsive shriek — the giant 
roared aloud, and bursting from the caravan 
with the dwarf clinging tightly round his neck, 



198 REWARD OF PRACTICAL JOKING. 

he jumped from the platform to the ground, 
where heaving his great chest, and staring 
wildly around, he looked like an infuriate heing 
from another world. Whether irritated by my 
laughter, or guided by an instinctive sense to 
the person of his tormentor, I know not, but 
leaping towards the hillock on which I stood, 
he snatched me in an instant from the ground. 
I now repented of my joke, for he clawed 
and shook me about as a cat does a mouse ; — a 
sound drubbing I would not have cared so much 
about, but the monster almost strangled me ; — 
his great hands squeezed me so that I thought 
every bone in my body was broken. Cry I 
could not, for he closed my mouth by main 
force, in order that I might be tortured with 
greater effect. He did not strike me, it is true ; 
if he had I think I must have died ; and in this 
forbearance he was generous, well knowing his 
own immense strength ; but having clawed me 
for a minute or two, he very coolly held me 
under one arm, my head towards the ground, 
and my feet kicking aloft ; while the dwarf on 
his shoulder was busily engaged in belabouring 
my back and sides with a cudgel; a task which 
he executed with great perseverance and effect, 
exerting at every blow his utmost strength; he 



THE GIANT NO DECEIVER. 199 

not being at all afraid of breaking my bones. 
Even this treatment was a relief to me, because 
I could cry. The people were panic-struck, 
and what with the horrible smell, and what 
with fear of the giant, no one came to my as- 
sistance ; indeed I did not deserve that they 
should. How the rest of the day passed I 
know only from hearsay : feverish and delirious 
I found myself two days afterwards in bed, sur- 
rounded by two doctors and a nurse. Six 
weeks passed, and I was yet unable to walk 
from the effects of my squeezes and bruises : 
however, I suffered no lasting injury, and I 
have many times since then been thankful that 
my fondness for practical joking experienced 
such a timely and salutary check. 

From what I have been told, the giant really 
looked as large outside the caravan as he did 
inside it, and he did not require the aid of stilts 
to increase his height. As to his strength I 
can offer personal testimony. But the sun has 
set, and I have reached my abode, therefore 
good night to you all. 



200 



LECTURE XVII. 

METALS. 

Having finished the description of non-metallic 
simple bodies, and the compounds which they 
form with each other, we now have to say a 
little about those which are metallic or metals. 
Ah ! there cannot be very much to remark con- 
cerning them, think you ; gold, silver, iron, tin, 
lead, and a few others will finish the list. No, 
no, the metals are not so soon done with ; there 
being no fewer than forty-one* of them, although 
perhaps you are not familiar with more than 
nine or ten. The ancients were only acquainted 
with seven. But what is a metal ? how shall 
we discover whether a substance be metallic or 
non-metallic ? This question has puzzled 
many greater philosophers than ourselves, and 
is not yet quite made out. We usually associ- 

" It has already been mentioned that the substance in 
these Lectures termed silicon is regarded by some persons 
as a metal, and termed by them silicium, in which case the 
number of the metals would be forty-two. 



BLOWPIPE DESCRIBED. 201 

ate with the term metal ideas of shining and 
very great weight ; but there are some which 
neither shine when polished, nor sink when 
thrown into water. Metals are fused or melted 
with greater or less difficulty, the common tem- 
perature of the atmosphere being sufficient to 
melt quicksilver, while the metal platinum can- 
not be fused by the strongest heat of a furnace, 
although the action of a galvanic battery melts 
it like wax in the flame of a candle : so also 
does the little flame of an oxy-hydrogen blow- 
pipe. By the bye, I must describe to you the 
nature of a blowpipe. In performing opera- 
tions which require a high degree of heat," 
manufacturers on the large scale are obliged to 
have recourse to furnaces ; but philosophic che- 
mists who operate on smaller quantities very 
often dispense with furnaces altogether, 
and employ as a substitute the flame of a 
common candle. You are incredulous, I 
see, but I must tell you the heat of the 
flame is increased to an enormous extent, 
by means of an instrument called the blow- 
pipe, which is a bent metallic tube, ter- 
minating in a very fine jet. 

It is used for the purpose of blowing the 
flame of a candle upon any substance which 



202 OXY-HYDROGEN BLOWPIPE. 

one may require to be exposed to a high degree of 
heat, either for the purpose of melting or other- 
wise. When a very large flame is required a 
lamp with a large wick must be substituted 
for a candle, and a pair of double bellows for 
the mouth. Of this description is the blowpipe 
used by those who work in glass. 

If the heat be required exceedingly violent, 
then an instrument called the oxy-hydrogen 
blowpipe is employed, which is a contrivance 
for burning with safety a mixture of oxygen 
and hydrogen gases. This mixture would ex- 
plode violently were it not for a very inge- 
nious expedient founded on the principle of 
Davy's safety lamp. If one layer of wire gauze 
be sufficient to intercept the flame of a gas, no 
more explosive than fire-damp, then it is but 
reasonable to infer that a greater number of 
layers would be able to intercept the flame of 
a much more explosive gas. 

This is the principle of the oxy-hydrogen 
blowpipe ; the mixed gas being forced through 
a great number of layers of wire gauze, — be- 
yond which the flame cannot pass. Instead of 
wire gauze, there is now employed another and 
a better substitute ; but its principle of action 
is exactly similar to that of the wire gauze. 



METALS UNDECOMPOSABLE. 203 

Well, this description of blowpipes is a slight 
digression : let us return again to our subject. 

Some metals by fusion may be made to unite 
together, and form a compound dissimilar in 
properties to either of its constituents : such 
compounds are termed alloys ; but the union of 
mercury with any other metal is termed an 
amalgam. Brass is an alloy of copper and 
zinc ; bell-metal of copper and tin ; and pewter 
of tin and lead. The metals are all of them, 
so far as is known, simple, or undecomposable 
substances, therefore, however much they may 
be altered in appearance by combination with 
other substances, still it is impossible to change 
one metal into another, and therefore the trans- 
mutation of common metals into gold is be- 
yond all human power. Tf the alchemists had 
arrived at this conclusion they might have 
saved themselves much fruitless labour and 
anxiety. 

Some metals can be beaten out into thin 
leaves, and hence are called malleable ; mal- 
leus being the Latin word for hammer. A single 
grain of gold may be made, by hammering, 
large enough to cover a space of fifty square 
inches ; or in other words, would be quite 
sufficient to gild a large tea-table. Some metals 
are brittle, like antimony : others, can be drawn 



*204 METALS OF THE ANCIENTS. 

into wires, and hence are said to be ductile. 
From a consideration of these properties, metals 
may be divided into a great number of classes ; 
but the most modern classification of metals is 
formed from a consideration of their chemical 
pecularities. I shall follow the historical ar- 
rangement, and speak of metals in the order of 
their discovery. 

Although there are now known no less than 
forty-one metals, yet the ancient Greeks and 
Romans were only acquainted with seven ; gold, 
silver, mercury, copper, lead, tin, and iron. 

Metals for the most part are obtained from 
under the surface of the earth, and here we 
cannot fail to be struck with a beautiful pro- 
vision of nature ; if instead of under the earth, 
great masses of metal had been placed on its 
surface, then there could not have been any 
beautiful green fields, but all now so lovely, 
would have then been barren and desolate. 

No metals, when in a pure state, can be dis- 
solved by water ; but all of them forrn soluble 
compounds, in which the metals are capable of 
being discovered by appropriate tests. 

NAMES OF THE METALS. 

Gold, Iron, Mercury, 

Silver, Copper, Lead, 



LIST OF THE METALS. 



205 



Tin, 

Antimony, 

Zinc, 

Bismuth, 

Arsenic, 

Cobalt, 

Platinum, 

Nickel, 

Manganese, 

Tungsten, 

Tellurium, 

Molybdenum, 



Uranium, 

Titanium, 

Chromium, 

Columbium, 

Palladium, 

Rhodium, 

Iridium, 

Osmium, 

Cerium, 

Potassium, 

Sodium, 

Barium, 



Strontium, 

Calcium, 

Cadmium, 

Lithium, 

Zirconium, 

Aluminium, 

Glucinium, 

Yttrium, 

Thorium, 

Magnesium, 

Vanadium. 



Gold. — Gold seems to have been known 
from the most remote ages, and at this circum- 
stance we cannot be much surprised ; for unlike 
most other metals which are generally dug from 
the earth in an impure state, gold more gene- 
rally occurs quite pure, and fit for working. In 
many regions it is found either on the surface 
of the earth or at a very inconsiderable dis- 
tance below it. Unskilful nations, then, who 
had not learned the method of extracting me- 
tals from their ores, might yet be struck with 
the appearance of shining gold, which they 
could, without much difficulty, beat or melt 
into various useful or ornamental shapes. There 



206 DESCRIPTION OF GOLD. 

are few countries which have not at some pe- 
riod or another yielded gold; the greatest 
quantity of the metal, however, is brought from 
South America and Africa, but Hungary, 
Sweden, and Norway yield it in smaller quan- 
tities, nor must we forget our own isles. In 
Cornwall there have very frequently been found 
small grains of gold, to a very considerable 
extent ; but in Ireland, in the county of Wick- 
low, there were formerly worked gold mines, and 
gold was once found so abundant in Scotland ; 
that at the nuptials of James the Fifth, covered 
dishes filled with Scotch gold were presented 
to the guests by way of dessert. 

Near Pamplona in South America, single 
labourers have collected upwards of two hun- 
dred pounds worth of gold grains in a day, and 
in the province of Sonora, the Spaniards dis- 
covered a plain fourteen leagues in extent, in 
which they found gold-wash at a depth of only 
sixteen inches. The grains were of such a 
size that some of them weighed seventy-two 
ounces, and in a very short time a few labourers 
had collected so much gold as was equal in 
value to more than thirty-one thousand pounds 
of our money. 

Gold never rusts or combines with oxygen 



DESCRIPTION OF SILVER. 207 

by exposure to air, and hence it is admirably 
adapted for the purpose of making coins. It 
may however be made to combine with oxygen 
by an artificial process, and the result is oxide 
of gold. Although this metal does not rust or 
tarnish by exposure to the air, yet by an arti- 
ficial process it may be made to combine with 
oxygen in three proportions, also with chlorine, 
iodine, and sulphur. It was this indestructi- 
bility of gold which induced the alchemists to 
employ it as an ingredient of the universal 
elixir, by the administration of which they 
hoped to render man immortal. If gold be in- 
destructible, thought they, we can eat and drink 
enough of it to become indestructible our- 
selves : but the alchemists were wrong, as they 
in due time discovered. 

Silver. — This is a beautiful white metal, 
too well known to require a minute descrip- 
tion. It is obtained from South America, Hun- 
gary, and various other parts of the world; not 
to mention our own isles, where it is found in 
combination with lead. Silver, like gold, is 
incapable of rusting or tarnishing by exposure 
to the air, and hence is well adapted for the 
purposes of current coins ; but the Romans 
did not employ silver for this purpose until the 



208 MERCURY ORIGIN OF ITS NAME. 

four hundred and eighty-fifth year of their city, 
up to which period they only used copper. 
When quite pure, silver is so soft that it may 
be cut with a knife ; and it cannot be used for 
the purposes of coining or jewellery, until it 
has been mixed, or alloyed, with a certain 
quantity of some other metal. English silver 
coins contain a small portion of copper. 

Although silver is not capable of rusting or 
oxidation by mere exposure to the air, yet by 
artificial means it may be made to combine with 
oxygen, chlorine, iodine, bromine, and sulphur. 

Mercury or Quicksilver. — This is a very 
curious metal, being always liquid at common 
temperatures ; although by intense cold it may 
be frozen, and when solidified it is malleable. 
In the neighbourhood of Hudson's Bay, this 
metal has been beaten out into leaves as thin 
as paper. The term mercury was applied to 
quicksilver by the alchemists, who called it after 
the winged messenger of the gods, because of 
the ease with which it is driven into vapour, 
or volatilised by the application of heat. 

There are some metals with which mercury 
is very prone to unite, and the combination of 
the two is termed an amalgam. If I rub a 
little mercury upon a sixj^ence, the latter as- 



MERCURY NATURAL HISTORY OF. 209 

sumes a glaring white aspect, arid feels as if it 
were smeared with oil. Very slight force would 
now be sufficient to break it in pieces ; but if 
I heat it in the flame of a spirit-lamp, fumes 
of mercury are seen to arise, and the sixpence 
is restored to its original condition. 

This property of mercury is taken advantage 
of in the silver-mines of South America and 
Hungary. The ore as it comes from the mine 
is mixed with mercury, which combines with 
the silver alone, and leaves the impurities be- 
hind. An amalgam of silver is thus formed, 
from which the mercury is obtained by distilla- 
tion, and the silver obtained quite pure. 

Mercury is found in Peru, the East Indies, 
Almaden in Spain, and Idria in Lower Austria; 
also in Hungary, Sweden, and China. Spain 
furnished mercury so abundantly, that in the 
year 1717 there remained above one thousand 
two hundred tons of it in the magazines of 
Almaden, after the necessary quantity had been 
exported to Peru for the purpose of extracting 
silver from the ore. But Peru yields quick- 
silver of its own ; its largest mine being that 
of Guanca Velica, which is one hundred and 
seventy fathoms in circumference, and no less 
than four hundred and eighty deep. In this 



210 COPPER — NATURAL HISTORY OF. 

immense cavity are houses, streets, and even a 
chapel for the performance of religious cere- 
monies. The miners are chiefly criminals, 
who, immured naked in this dreary abode, 
very soon die of the most horrible convul- 
sions. 

Mercury combined with sulphur, as a sul- 
phuret of mercury, called cinnabar, is found as 
a natural product ; by artificial means the me- 
tal may also be made to combine with oxygen, 
chlorine, iodine, bromine, and cyanogen. The 
substance called calomel, and so much used in 
medicine, is a J/chloride of mercury, or a com- 
pound of two atoms chlorine, with one of the 
metal. 

Copper. — Copper is a metal of a reddish 
colour, too well known to require a minute de- 
scription. The ancient Greeks and Romans 
were well acquainted with it, and applied it to 
many uses for which we now employ iron. 
The most ancient copper-mines were in the 
isle of Cyprus, and it is now found in North 
America, Sweden, China, Japan, Sumatra, 
North of Africa, also in Cornwall, and the Isle of 
Anglesea, in England. English copper-mines 
have not been worked more than one hundred 
and sixty or one hundred and seventy years ; 



TESTS FOR COPPER. 211 

before that period, whenever the workmen met 
with copper they threw it away as useless. So 
very cheap is copper in Sweden, that houses 
are covered with it, — as indeed is the London 
Coliseum in the Regent's Park. 

Immense quantities of sheet-copper are used 
in our dock-yards for the purpose of sheathing 
the bottoms of ships, in order to protect them 
from the action of sea-water. All copper ves- 
sels, which are used for the purpose of prepar- 
ing food, should be kept remarkably clean and 
bright, because acid and fatty substances dis- 
solve the metal, and generate a most danger- 
ous poison. 

Solutions containing copper strike a blue 
colour with hartshorn, or solution of ammonia, 
and by this test the metal in solution may al- 
ways be discovered. 

Copper unites with oxygen in three propor- 
tions, two of which are found native, also with 
chlorine, iodine, sulphur, and phosphorus. 

Lead. — This metal abounds in Scotland, 
Northumberland, Durham, and Derbyshire ; 
some also is found in Devon. It was well 
known to the ancient Greeks and Romans, who 
applied it to a variety of purposes. Sheets of 
it fastened with nails of bronze were used to 



212 WATER RENDERED POISONOUS BY LEAD. 

sheathe the bottoms of ships, just as our ships 
are sheathed with copper. Leaden pipes were 
also used for the purpose of conveying water, 
although the architect Vitruvius, who flourished 
in the reign of Augustus, reprehends the plan 
as being dangerous, well knowing that water, 
under certain circumstances, might be contami- 
nated with the metal, and rendered poisonous 
in consequence. 

The ancient Greeks and Romans knew that 
harsh wines could be rendered mild by im- 
mersing in them a piece of lead ; but it was 
not known that the wines owed this mildness 
to the presence of a slow poison. During the 
first year of the Christian era, lead at Rome 
was twenty-four times as dear as it now is in 
Europe, whereas tin was only about eight times 
its present price. 

Lead combines with oxygen in four different 
proportions, also with chlorine, iodine, bro- 
mine, fluorine, sulphur, phosphorus, and car- 
bon. 

Tin.— This is a beautiful white metal which 
is applied to a variety of useful purposes. Tin 
is found in Cornwall, South America, and 
various parts of the East Indies. The Cornish 
tin-mines have been celebrated from a very re- 



TIN KNOWN TO HOMER. 213 

mote period. According to Aristotle, they were 
known in his time, and Diodorus Siculus, who 
wrote about forty years before Christ, gives an 
account of the method of working them. So 
renowned were the Cornish mines in the middle 
of the seventeenth century, that the celebrated 
Becher, a physician of Spire, and tutor of 
Stahl, came over from his native land, on pur- 
pose to visit them. Tin must have been known 
very early, as it is mentioned by Homer, and 
also in the book of Moses. An alloy of tin 
and copper was much employed by the ancients 
for the purpose of making edged tools, iron 
being at that time very expensive, and com- 
paratively scarce. 

Tin unites with oxygen in three proportions, 
also with chlorine, iodine, sulphur, and phos- 
phorus. 

Iron. — Iron is the most abundant, and cer- 
tainly the most useful of all the metals. It 
has been known from periods of very great an- 
tiquity, and was employed by the ancient Jews, 
Greeks, and Romans, although not to any 
great extent, on account, I suppose, of the dif- 
ficulty experienced in working it. 

From a perusal of the fourth, eighth, and 
eighteenth chapters of Deuteronomy, it appears 



214 IKON — mariners' compass. 

that iron was known in the time of Moses ; and 
during the period of the Trojan war, the Greeks 
were acquainted with the method of tempering 
it, as may be learned from a perusal of Homer's 
Odyssey, in which he describes the firebrand 
driven into the eye of Polyphemus as hissing 
like red-hot iron immersed in water. 

■" when arm'rers temper in the ford 

The keen-edged pole-axe, or the shining sword, 

The red-hot metal hisses in the lake, 

So in his eyeball hiss'd the plunging stake." 

Iron is usually extracted from ores which 
are dug out of the earth, sometimes however it 
has been found nearly pure, and in large masses 
on the surface of the earth. In the museum of 
the Academy of Sciences at Petersburgh, there 
is a mass of native iron twelve pounds in 
weight. Irou has the curious property of being 
attracted by the loadstone, or magnet; and 
pieces of iron or steel may themselves be ren- 
dered magnetic, when they always point north 
and south. On this principle depends the 
mariner's compass, by which a ship's course 
may be directed day after day, although far 
from the sight of any land. It is not precisely 
known who discovered this very useful instru- 



ANTIQUITY OF THE MAGNETIC NEEDLE. 215 

ment. Some call him Flavio Giojo; others 
Givi, a native of Amalfi in Naples, at the be- 
ginning of the fourteenth century ; but there 
are proofs that the use of the magnetic needle, 
in pointing out the north was known at an 
early period in Europe, and that a contrivance 
similar to a compass went under the name of 
marinette in France, as early as the twelfth 
century. The English first suspended the 
compass so as to enable it to retain always a 
horizontal position, and the Dutch gave names 
to the divisions of the card. The earliest mis- 
sionaries to China found the magnetic needle 
in use in that country. 

If two pieces of iron be made white hot and 
then hammered together they adhere, and form 
one piece. This operation is termed welding, 
and with the exception of platinum, is pos- 
sessed by no other metal. Iron is used in the 
two conditions of wrought and cast-iron ; the 
former is by far the purest variety, and is 
adopted for welding, but cast-iron can most 
easily be melted. I need not call your atten- 
tion to the uses of iron : without the beauty of 
certain other metals, it surpasses them all in 
utility, and if deprived of it we should be re- 
duced to a state of semi-barbarism. 



216 ANTIMONY ORIGIN OF THE TEEM. 

Iron combines with oxygen in three propor- 
tions: iron-rust is a peroxide of the metal. It 
also combines with chlorine, fluorine, bromine, 
iodine, sulphur, phosphorus, and carbon. Steel 
and cast-iron are both carburets of the metal. 
Steel is made by heating iron for a long time 
together in contact with pieces of charcoal. 

Antimony is a brittle metal of a bluish 
white colour. It is seldom found pure but 
combined with sulphur as a sulphuret of anti- 
mony, which compound was formerly mistaken 
for the metal itself. Antimony enters into the 
composition of printers' types, and its com- 
pounds are much employed in medicine. An- 
timony was first described in the year 1490 by 
Basil Valentine, one of the alchemists, and ac- 
quired its name from a very curious circum- 
stance. Valentine having administered some 
to pigs, found that it made them fat ; wishing 
to fatten his brother monks, he gave them some, 
too; but instead of fattening them it killed 
them ; hence the substance was called anti- 
mony, from anti, against or contrary to, and 
monachos, a monk. 

Antimony combines with oxygen in three 
proportions, forming the sesquioxide of anti- 
mony, antimonious, and antimonic acids. It 



BISMUTH, ZINC, ARSENIC. 217 

may be also made to unite with chlorine and 
iodine, while a combination of sulphur and an- 
timony is found largely in a natural condition. 

Bismuth occurs in nature, both simple and 
in combination. It is a reddish white metal, 
brittle and very fusible. With oxygen it forms 
two combinations ; with chlorine, bromine, and 
sulphur, one respectively : these I shall not 
stop to mention separately. 

Zinc combines with oxygen in two proportions, 
forming oxides ; it also unites with chlorine, 
iodine, fluorine, bromine, sulphur, and cyanogen. 

Zinc is a bluish white metal, which was first 
described by Paracelsus, in the sixteenth cen- 
tury. At certain temperatures zinc is a very 
brittle metal, but at others it is both malleable 
and ducile, which enables it to be rolled or 
hammered into sheets of considerable thinness. 

Zinc and copper may be made to combine 
together in several proyjortions, forming valu- 
able alloys. Brass consists of one part zinc to 
four of copper : when more zinc than this is 
used, then compounds are generated, which are 
called tombac, Dutch-gold and pinckbeck. 

Arsenic or Arsenicum is an exceedingly brittle 
metal, of a stronglustre, and white colour, running 
into steel-gray. If thrown upon a hot surface 
arsenic flies off into vapour, which possesses a 



213 COBALT ORIGIN OF THE TERM. 

garlic odour. That dreadful poison, known in 
the shops by the name of arsenic, and sold in 
the form of a white powder, is in reality a com- 
bination of the metal with oxygen, and is 
called arsenious acid ; besides this, there are 
two other combinations of arsenic with oxy- 
gen : it also unites with chlorine, iodine, bro- 
mine, and sulphur. White arsenic, or arsenious 
acid, is such an important substance, that we 
must very fully investigate its chemical proper- 
ties by means of tests ; but I think we had better 
finish our description of metals first, and then 
devote an hour or so to their tests alone. 

Cobalt is a brittle reddish grey metal, which 
derives its name from kobold, an evil spirit; 
because when combined with other metals, its 
presence renders them very difficult to be 
worked, and hence the superstitious miners 
thought that they were bewitched. Cobalt was 
long regarded with such horror as to give rise 
to the employment of a prayer, to the effect 
that miners might be protected from cobalt 
and all evil spirits. This metal, like iron, is 
attracted by the magnet, and may be rendered 
permanently magnetic. 

Cobalt unites with oxygen in several pro- 
portions, also with chlorine, sulphur, and phos- 
phorus. 



SYMPATHETIC INK. 219 

Chlorine of cobalt dissolved in water, is used 
as a sympathetic ink. I write with a little of 
this solution on a piece of paper : at present 
the traces of the pen are not seen, but on hold- 
ing the paper before the fire, every part which 
has been moistened by the chloride turns blue. 
Now the theory of this change is simple 
enough : chloride of cobalt possesses an affi- 
nity for water, when combined with this it is 
white, when the water is driven off the chloride 
is blue. Heat, then, by driving off the mois- 
ture effects the change which you observe. 

If the cobalt be contaminated by iron or 
nickel, then the resulting sympathetic ink will 
yield not a blue but a green colour, and this is 
the substance employed in making those ma- 
gic prints of trees, which in the cold appear 
leafless and bare, but when held before the 
fire, are adorned with the most luxurious foli- 
age. 

Nickel is a metal of a white colour, very hard 
and infusible, it is always a constituent of me- 
teoric iron, or such as falls from the sky. 
Where these meteoric masses come from has 
never been satisfactorily determined. Some 
persons believe them to be shot from volcanoes 
in the moon; others that they are little wander- 
ing planets, or fragments of planets ; — but with 



220 ORIGIN OF THE TERM OLD NICK. 

this question chemists have nothing to do : we 
know that large masses of iron frequently have 
fallen upon the surface of the earth, and they 
have invariably contained the metal nickel. 

However, we do not obtain it from this source, 
it is got from a copper-coloured mineral, called 
in German kupfer-nickel, or base copper, be- 
cause the miners tried in vain to get copper out 
of it, and therefore thought it was bewitched. 
Perhaps this very word nickel may have given 
origin to our term " Old Nick." 

Platinum is the heaviest of all the metals, 
and a very valuable substance. In appearance 
it very nearly resembles silver; indeed, the 
word platiwa, by which it is sometimes known, 
means little silver, being the diminutive of 
plata. It cannot be melted by the strongest 
heat of a furnace, but, like iron, it is capable 
of being welded. Platinum is not acted upon 
by the strongest acids, nor does it tarnish or 
rust by exposure to the air. It occurs in Bra- 
zil, Peru, and other parts of South America, 
generally in the form of flattened grains, which 
are rarely so large as a pea : however, it has 
lately been found traversing rocks in the form 
of veins, and there have recently been disco- 
vered valuable mines of it in the Uralian moun- 
tains. 



MANGANESE PALLADIUM. 221 

Platinum unites with oxygen, chlorine, iodine, 
and sulphur. 

Manganese never occurs native, but exists 
always in combination with oxygen, with which 
element it unites in no less than seven different 
proportions. The black, or peroxide of man- 
ganese occurs in various parts of the world. 
Sweden yields it in great abundance, and I 
need not remind you of the manganese-mines 
of Cornwall and Devon. A large quantity is 
also obtained from the Mendip-hills, in Somer- 
setshire. 

The black oxide of manganese we have 
already had occasion to use in the preparation 
of oxygen and chlorine : for the latter purpose 
a great quantity is employed by bleachers. 

Palladium. — Rhodium, iridium, and osmium 
are found mixed with grains of native platinum. 
Palladium is so called from the planet Pallas. 
Rhodium from rhodon, a rose, because of the 
rose-colour possessed by its compounds: iridium 
from iris, the rainbow, because of the various 
tints assumed by its various salts ; and osmium 
derives its name from osme, smell, because its 
compounds have all a very strong odour. 

And now, passing over a great many metals, 
the names of which you may see by the dia- 



222 POTASSIUM, SODIUM, LITHIUM. 

gram, I come to a most extraordinary class in- 
deed, — the class of alkaline metals. Ever since 
the first commencement of chemistry in Arabia, 
the term alkali, itself of Arabian origin, has 
been applied to the substances, soda, potash, 
and ammonia ; lately the alkali lithia has been 
added to the number. I have proved to you 
that ammonia is a compound of nitrogen and 
hydrogen : its composition has been long 
known, but potash, soda, and lithia were at 
the same time imagined to be simple, or unde- 
composable substances. Judge, then, what 
was the surprise of the chemical world, when 
Sir Humphry Davy proved that those three 
alkalies were the rusts or oxides of as many 
different metals, which metals he obtained in a 
separate state. They have been named potas- 
sium, sodium, and lithium : the latter I have 
never seen, but I can show you specimens of 
the two others. 

I have already had occasion to notice the 
vast power with which the voltaic battery is 
endowed in separating the elements of certain 
compounds. Water, when submitted to its 
agency, is resolved into hydrogen and oxygen, 
as I have already shown you : well, in like 
manner, potash, when galvanized, is resolved 



METALS WHICH ARE LIGHTER THAN WATER ! 223 

into potassium and oxygen ; soda into sodium 
and oxygen, lithia into lithium and oxygen. 
Such is the method by which those metals were 
first prepared, but more recently there has been 
discovered a plan which is more easy to con- 
duct, and which yields them in greater quantity. 
Potash, soda, and lithia, then, are merely the 
rusts or oxides of the three metals : potassium, 
sodium, and lithium, which have all such an 
excessive affinity for oxygen, or, if I may be 
permitted to use the term, such a desire to unite 
with oxygen, that their preservation becomes a 
matter of considerable difficulty. Lithium I 
have never seen, but here are specimens of po- 
tassium and sodium; you will remark that they 
are immersed in a fluid ; this fluid is called 
naptha, and does not contain any oxygen, which 
circumstance renders it well adapted for our 
purpose. We are always accustomed to asso- 
ciate with metals the idea of great weight, yet 
potassium, sodium, and lithium, notwithstand- 
ing their metallic lustre, are all of them lighter 
than water. 

I will now show you the metallic properties 
of potassium, for which purpose I take a little 
out of the bottle and cut it with a knife. See 
how bright and shining the cut surface appears ; 



224 WATER SET ON FIRE ! 

in this respect it bears no distant resemblance 
to silver ; but it has already tarnished or be- 
come oxidized from exposure to air, and the 
white covering which collects upon its surface 
is potash. The most wonderful property of 
potassium is that it takes fire immediately on 
touching water ! or, to speak more correctly, it 
sets the -water on fire — yes, actually sets the 
water on, fire ! therefore if we could find a suf- 
ficient quantity of potassium, the sea itself 
might be burned. I now throw a little bit of 
potassium upon some water in a basin ; and see 
what results : the metal kindles into flame with 
an explosion, hissing and shining, it darts 
across the water like a little meteor, decreasing 
rapidly in size, it moves quicker and still 
quicker, — now it shoots around the basin, now 
across it ; now it moves in circles, now it dashes 
about in irregular zig-zags : pop ! and it is 
gone. Let us ascertain what has become of it. 
Water, you know, is composed of oxygen 
and hydrogen, united together with a certain 
degree of force. Now combustion is nothing 
more than violent chemical action, attended 
with the evolution of light and heat. Oxygen 
is generally concerned in those violent chemi- 
cal actions, and hence oxygen is one of the 



COMBUSTION EXPLAINED. 225 

chief supporters of combustion. For instance, 
the ordinary combustion of a piece of charcoal 
is merely a rapid union of carbon with oxygen 
of the air. But if oxygen alone be required, 
why is it that charcoal cannot burn under wa- 
ter ? The explanation is simply this : — atmo- 
spheric oxygen is uncombined, or, at all events, 
the combination is very slight ; consequently, 
it may be regarded in the light of an indivi- 
dual who is perfectly free to do as he likes, and 
therefore no obstacle is opposed to its uniting 
with carbon, or the matter of charcoal. But 
the oxygen of water is in a very different pre- 
dicament. We may regard it as a prisoner 
held in fetters by its gaoler, hydrogen ; or we 
may fancy it a husband under the control of a 
self-willed and domineering wife ; or, not to 
push our similes further, it may be compared 
to any other personage who cannot have his 
own way ; in short, it cannot unite with car- 
bon like the free and uncombined oxygen of 
the air. Carbon may try to get oxygen away 
from hydrogen, but all invain. Potassium, how- 
ever, is stronger than carbon ; therefore when 
thrown upon water it separates oxygen from hy- 
drogen by main force, and combining with it 
rapidly, gives rise to combustion ; while potash 

Q 



226" TESTS FOR AN ALKALI. 

is formed and dissolves in the remaining water. 
The liberated hydrogen uniting with a little 
potassium forms a spontaneously inflammable 
gas, called " potassiuretted hydrogen." The 
water in the basin has now acquired a hot, 
burning, peculiar taste ; I find that it renders 
yellow turmeric-paper brown, and restores the 
original blue colour to litmus-paper which has 
been reddened by an acid : these are properties 
of an alkali : in short, the water now contains 
the alkali, potash. 

I need not go through the same process with 
the metal sodium ; it is sufficient for me to 
mention, that, like potassium, it decomposes 
water with great rapidity, but does not usually 
give rise to combustion, except the water be so 
thickened by the addition of gum that the so- 
dium cannot roll about. 

I need scarcely tell you that potassium, pos- 
sessing, as it does, such a violent affinity for 
oxygen, cannot exist in a free or uncombined 
state ; combined, however, with oxygen in 
the form of potash, we find it in the animal, 
vegetable, and mineral kingdoms. Our own 
bodies contain it ;* land-plants contain it ; and 
among minerals wdiich have potash entering 

* Sodium, however, enters much more extensively into 
the composition of animals than potassium. 



POTASH HOW OBTAINED. 227 

into their composition, I may mention the sub- 
stance called felspar, which is a constituent of 
granite. Potash is usually obtained from the 
ashes of land-plants by the following process. 
These ashes contain carbonate of potash, or 
the alkali united with carbonic acid ; a watery 
solution of which carbonate of potash is ob- 
tained by washing. To this solution lime is 
now added ; carbonate of lime subsides, and 
potash is left dissolved in water ; which, by the 
application of heat, may be driven off in va- 
pour, potash alone remaining.* See how very 
shortly all these changes or decompositions, as 
they are called, may be expressed by means of 
a diagram. 

Carbonate of f Potash (set free.) 

( Carbonic Acid 

Lime -^Carbonateof Lime. 

Potassium unites with chlorine, forming the 
chloride or chloruret of potassium : with iodine 
constituting the iodide or io&uret, with bromine 
the bromide or bromuret, and with fluorine the 
fluoride or ftnoraret of potassium ; each of 

* Strictly speaking, a small portion of the water cannot 
be driven off even by the strongest possible heat, but re- 
mains in chemical union with the alkali. 

Q2 



'228 SOURCES OF COMMON SALT. 

which has its own uses either in the practice of 
medicine or the arts 

Sodium, like potassium, unites with various 
simple substances ; but I shall only speak of 
chloride or chloruret of sodium, which is com- 
mon table-salt. This substance I need not tell 
you exists largely as a constituent of sea-water; 
indeed most countries are supplied with it from 
this source alone, but England derives its salt 
from mines situated in Cheshire, Worcester- 
shire and Shropshire. 

Chloride of sodium may be generated by 
burning sodium in chlorine gas ; also by add- 
ing hydrochloric or muriatic acid to soda, or 
carbonate of soda. I will suppose carbonate 
of soda to be used, in which case the decom- 
position is shown by this diagram. 

( Carbonic Acid (escapes.) 

Carbonate of ) 

Soda } goda < Oxygen Water. 

v ( feodum ' 

Hydrochloric^ H y Jr °S en \ 

(.Chlorine Chloride of 

Sodium. 

Formerly it was imagined that hydrochloric, 
or muriatic acid, and soda united together di- 
rectly ; and on this supposition common salt 
was called hydrochlorate or muriate of soda : — 



ALKALINE EARTHS. 229 

indeed, it is not long since that the very term 
salt was exclusively applied to substances pro- 
duced by the union of acids, either with me- 
tallic oxides, or with the alkali, ammonia ; and 
since the discovery of the true nature of com- 
mon salt, its very claim to the term salt has 
been disputed : indeed, many chemists of the 
present day, regardless of the violation they 
offer to ordinary language, assert that common 
salt is no salt at all. 

Before the time of Sir Humphry Davy, not 
only were the alkalies potash, soda, and lithia 
imagined to be simple bodies, but also the 
substances known by the name of earths. 
Earths are divided into alkaline earths, or those 
which in some degree resemble alkalies, and 
the non-alkaline earths. The alkaline earths are 

Baryta, 

Strontia, 

Lime, 

Magnesia. 
The non-alkaline earths are 

Alumina, 

Thorina, 

Glucina, 

Zirconia, 

Yttria. 



230 COMPOSITION OF ALKALINE EARTHS. 

After it had been proved that the alkalies, 
potash, soda, and lithia were metallic oxides, 
the idea was not very improbable that alkaline 
earths might have a similar composition. Ex- 
periment soon settled this point. Baryta was 
found to be the oxide of a metal since called 
barium ; strontia the oxide of a metal called by 
its discoverer strontium ; lime, the oxide of cal- 
cium ; and magnesia of magnesium. The five 
non-alkaline earths have been also found to 
possess a similar constitution ; they are oxides 
of the metals aluminium, thorinium, glucinium, 
zirconium, and yttrium respectively : metals 
which are only obtained by tedious chemical 
processes, and which I have never seen. 

About the earths I have not much to re- 
mark. Baryta and its soluble compounds are 
valuable tests for sulphuric acid, with which 
they throw down an insoluble sulphate of baryta. 
Strontia derives its name from Strontian in 
Scotland. Lime is found in the animal, vege- 
table, and mineral kingdoms : it is usually ob- 
tained by exposing chalk or marble, which 
are carbonates of lime, to a strong heat ; car- 
bonic acid is expelled, and lime in a pure state 
remains. (See p. 147.) Magnesia is obtained in 
a similar manner from carbonate of magnesia. 



IMPORTANCE OF THE METALS. 231 

I now conclude the subject of metals, and T 
am sure it is quite unnecessary for me to remind 
j r ou of their immense importance in the grand 
economy of nature as well as in the arts of civilized 
life. Suppose we were deprived of iron alone : 
what misery, what confusion would result, and 
to what primeval barbarism should we be again 
plunged : no ploughshares to cultivate the 
ground ; no swords to repel our foes ; no vast 
machinery to abridge our labours, and multiply 
our riches ; no compass to direct the mariner 
across the deep : half the genius, the wisdom, 
the intellect imparted by the Almighty to man- 
kind, would have no scope for its exercise, 
and we should be little removed from those 
primitive savages who lived upon acorns and 
wild berries. But why do I talk thus ? — with- 
out iron we could not have existed, for it en- 
ters into the composition of our blood. 



232 



LECTURE XVIII. 

SUBSTANCES WHICH ARE FORMED BY THE UNION 
OF COMPOUNDS WITH EACH OTHER. 

Our labours in chemistry are drawing towards 
a conclusion, and I shall very soon bid the sub- 
ject farewell : it was never rny intention to en- 
gage you very deeply in the science, but merely 
to take a passing glance at its wonders, and its 
beauties 

We have hitherto regarded simple bodies as 
combining together and forming compounds ; 
but we have taken no account of the combina- 
tions which occur between compounds them- 
selves : of these there are a very large num- 
ber, and the nature of some of them is not 
at all easy for a beginner to understand. Their 
composition was formerly much more difficult 
to remember than at the present time, because 
chemical substances were named after no fixed 
rule, but only according to the whim and 
caprice of their discoverers. 



CHEMICAL NOMENCLATURE EXPLAINED. 233 

Amongst the successful labours of modem 
chemists the method of naming substances in a 
manner to indicate their composition stands 
high in the scale of practical utility. You may 
already have formed some idea of its impor- 
tance, although I have not directed your atten- 
tion exclusively to the matter. The term chlo- 
rine indicates that the gas is greenish ; hydro- 
gen means the water-former, and oxygen the 
acid-former, because chemists imagined that 
every acid contained it. This opinion is in- 
correct, since every acid does not contain it ; 
yet the greater number do, and therefore the 
term oxygen may still be retained with con- 
siderable propriety. 

It is always taken for granted that an acid 
contains oxygen, except the contrary be ex- 
pressed. By the term sulphuric acid I under- 
stand an acid composed of sulphur and oxygen, ; 
by /?yrf/"0-sulphuric acid, an acid composed of 
sulphur and hydrogen. When oxygen only 
forms two acids with a substance, then the 
name of the acid which contains the smaller 
proportion of oxygen is made to end in ous : 
and of the one which contains the larger pro- 
portion of oxygen in ic. If there should exist 
more than two combinations, then we are 



•234 CHEMICAL NOMENCLATURE EXPLAINED. 

obliged to have recourse to Greek and Latin 
words. I may illustrate what I mean by re- 
ferring to the compounds of sulphur and oxy- 
gen. Formerly only two such compounds were 
known ; one composed of one atom sulphur 
and two atoms oxygen, and the other of one 
atom sulphur and three atoms oxygen; the 
former was called sulphurous, and the latter 
sulphuric acid. More recently there have been 
discovered two other compounds of oxygen and 
sulphur ; one of which contains less oxygen 
than sulphurous acid, and the other more oxy- 
gen than sulphurous, but less than sulphuric 
acid ; hence they are respectively called hypo- 
sulphurous and hypo-sviphwdc acids ; hypo, or 
upo, meaning under or less. In this diagram 
the two original compounds of sulphur and 
oxygen are represented by capitals ; the two 
others by small Roman letters. 



Hypo-sulphurous Acid 
SULPHUROUS ACID 
Hypo-sulphuric Acid 
SULPHURIC ACID 



Sulphur. 

2 


Oxygen. 


2 


1 


2 


2 


5 


1 


3 



Now, before the introduction of this new no- 



CHEMICAL NOMENCLATURE EXPLAINED. 235 

menclature, sulphuric acid was known by the 
name of oil-of-vitriol ; a name which gives us 
no useful information whatsoever, indeed it 
misleads us, for the so-called oil-of-vitriol is no 
oil at all. 

If an acid whose name ends in ic combine 
with a substance, the name of the compound 
is made to terminate in ate: for instance, sul- 
phur/e acid with soda forms sulphate of soda. 
If an acid whose name terminates in ous com- 
bine with a substance, then the name of the 
resulting compound is made to terminate in 
ite : for example, sulphuvoMS acid with soda 
forms sulph/fe of soda. When a simple sub- 
stance unites with oxygen, and does not form 
an acid, the compound is simply termed an ox- 
ide. In like manner the combination of iodine, 
chlorine, bromine, sulphur, and fluorine, with 
other simple substances, forms chlorides or 
chlorurets, iodides or iodurets, bromides or 
brornurets, sulphides or sulphurets, and fluo- 
rides or fluorurets. But the advantages of the 
new system of nomenclature are best displayed 
by some other examples which I now mean to 
give you. 

The chemist, Glauber, discovered a salt, 
which was long known by no other appellation 



236 CHEMICAL NOMENCLATURE EXPLAINED. 

than Glauber's salt ; but this name conveys 
very little useful information indeed ; — merely 
giving us to understand that Glauber was, in 
some manner or another, connected with it ; a 
matter of very slight importance. Now 
Glauber's salt being a compound of sulphuric 
acid with soda, the framers of the new nomen- 
clature called it sulphate of soda, a term which 
immediately bespeaks its composition, and af- 
fords us a very useful piece of information. 

Again, there exists a substance commonly 
known by the name of sal-ammoniac; but what 
information does this convey ? none at all : 
whereas the term hydrochlorate of ammonia, 
informs us that it is a compound of hydro- 
chloric acid and ammonia. Having now made 
such remarks upon the system of chemical 
nomenclature as are necessary for you to be 
acquainted with, I bring the subject to a con- 
clusion. Its consideration may not appear a 
very agreeable study, but it is nevertheless a very 
useful one, and will enable you to overcome 
many of the apparent difficulties in chemistry. 
I am sure, then, you will not refuse to devote a 
little time and attention to the purpose of ac- 
quiring it. Remember, a child does not derive 
much pleasure in learning his alphabet, yet it 



MEANING OF THE TERM SALT. 237 

would be a pity indeed that he should be de- 
barred from all the riches of literature and 
science, merely because of the annoyance to 
be endured in first learning his letters. 

Among the various substances which are 
generated by the union of compounds with each 
other, the class of bodies called salts is by far 
the most important : and yet if you ask me 
what I mean by the term salt, I confess I can- 
not very well answer you ; it is a point on 
which chemists are not exactly agreed. If I 
add sulphuric acid to soda, sulphate of soda re- 
sults ; if I add nitric acid to the same alkali, I 
obtain nitrate of soda ; both of these substances 
are termed salts, and the alkali soda is said to 
be their base. By adding hydrochloric acid to 
soda, common table-salt is obtained ; which 
substance chemists for a long time considered 
to be hydrochlorate of soda, but now it is known 
to be chloride of sodium, or a direct union of 
chlorine with sodium. Hydrochloric acid is 
not the only one which does not unite directly 
with bases, for hydriodic acid, hydrobromic 
acid, and, in short, all the hydracids demean 
themselves in a similar manner. Still those 
acids yield compounds in appearance and 
general properties very much resembling salts, 



238 INDIVIDUAL SALTS EXAMINED. 

which are formed by the union of an acid with 
a base. The question, then, resolves itself into 
this — shall the chlorides, iodides, bromides, and 
fluorides be called salts, or shall they not ? 
Well, it is not for me to determine this point, 
but I think it rather a startling assertion to af- 
firm that common table-salt is no salt at all. 
However, we need not teaze ourselves about a 
mere definition : whether common salt be really 
a salt, chemically speaking, or no salt at all, it 
is nevertheless chloride of sodium, and we may 
ascertain its properties just as well under one 
name as another. 

I have already said what I consider necessary 
about chloride of sodium, as well as some other 
disputed salts ; therefore we will now investi- 
gate the properties of a few of those substances 
which every one admits to be salts, as being 
composed of an acid and a base. 

Nitrates, or combinations of nitric acid with 
bases. 

As one of the most important of the nitrates, 
I may mention the nitrate of potash, called also 
saltpetre, or nitre : and now, in order to give 
you a true idea of the composition of this salt, 
I will go through the process of making it. 

First, then, I add nitric acid, much diluted 



NITRATE OF POTASH — HOW MADE. 239 

with water, to carbonate of potash ; pure potash 
would do but it is very expensive, and carbonate 
of potash answers just as well. The mixture 
hisses and bubbles like a glass of soda-water, 
because nitric acid seizes the potash, and sets 
carbonic acid, in the form of gas, at liberty. 
The effervescence or bubbling has ceased, and 
the solution contains nitrate of potash. This 
nitrate of potash cannot be converted into 
vapour by heat, although water can ; therefore, 
if I make the solution hot, water is driven oft* 
in the form of vapour, and nitrate of potash re- 
mains behind : if the heat be applied too long, 
the salt is obtained in a shapeless mass ; but if 
the heat be discontinued as soon as a pellicle 
is seen to form on the solution, then we get 
nitrate of potash in crystals. There are several 
methods of crystallizing bodies, but the most 
usual way is by the process of evaporation. 

Nitrate of potash is a most valuable salt, and 
we should be badly off indeed if it could only 
be made by adding nitric acid to carbonate of 
potash. It is used both in medicine and the 
arts. Gunpowder is a mechanical mixture of 
nitre, sulphur, and charcoal. In various parts 
of the world great quantities of nitre exist as a 
natural product. We derive our supply of it 



240 IMPORTANT DISCOVERY OF BERTHOLLET. 

from the East Indies, but a great proportion of 
that employed in France and Sweden is made 
artificially, not in the way I have shown you, 
but by exposing certain mixtures of animal and 
vegetable substances to the action of the air. 
This method of obtaining nitre was a discovery 
of the celebrated French chemist, Berthollet. 
France at one period of the revolution was nearly 
prevented from carrying on war against her ene- 
mies, on account of a deficiency of nitre. Like 
England, she had been accustomed to receive 
her supply from the East Indies, but at the 
period to which I allude, her intercourse with 
those regions was prevented by the vigilance of 
the English fleet. Matters were in a most pre- 
carious state, and Bonaparte applied to his 
philosophers for assistance. The application 
was not in vain ; nitre was made at home in- 
stead of being imported from abroad, and dur- 
ing a great number of years France was sup-' 
plied with this article by her own manufac- 
tories. 

Nitric acid when united with soda forms 
nitrate of soda ; with ammonia, nitrate of am- 
monia. 

There are but few metals which do not yield 
each an oxide capable of uniting with acids 



NITRATES. 241 

and thus becoming the base of a salt. We have 
already seen that potash, or the oxide of potas- 
sium, combines with nitric acid, forming nitrate 
of potash. In like manner it unites with oxide 
of silver and oxide of copper, forming nitrate of 
oxide of silver, and nitrate of oxide of copper 
respectively : also with oxides of other metals, 
forming as many different nitrates. It is more 
usual to say nitrate of silver, nitrate of copper, 
and so on, than nitrate of oxide of silver, nitrate 
of oxide of copper : this omission, however, is 
merely for the sake of abbreviating a long name ; 
and now I wish you to remember that acids 
never combine with metals, but with oxides of 
metals. 

Nitrate of silver is thus made. Pour upon 
the metal silver some nitric acid mixed with 
water. Violent chemical action immediately 
ensues. Silver in the first place takes oxygen 
from nitric acid to form oxide of silver, w 7 hich, 
combining with undecomposed nitric acid forms 
nitrate of the oxide of silver, and binoxide of 
nitrogen escapes. 

C Nitrogen ..Binoxide of Nitrogen Jesmpes.) 

Nitric Acid -' Oxygen 



Oxygen \ 

_>Oxide of Silver. 



_Vitrate of Oxide of Silver. 
Nitric acid_ 



J-Nit 



242 ACIDS RESEMBLING NITRIC ACID. 

By the process of evaporation nitrate of silver 
may be obtained in crystals, and these crystals 
when melted, form lunar-caustic, a substance 
much used by surgeons. A solution of nitrate 
of silver stains animal and vegetable substances 
of an indelible black ; hence it is employed for 
the purpose of marking linen, and also to 
blacken red hair and whiskers ; however, it 
blackens the skin no less than the hair, which 
circumstance has caused hair-dressers to invent 
other dyes which are free from this objec- 
tion* 

Nitrate of copper may be prepared in the 
same manner as nitrate of silver, merely sub- 
stituting one metal for the other. 

Most of you know that touch-paper is made 
by drying paper which has been dipped in 
nitrate of potash. Now any salt which is ca- 
pable of making touch-paper, must be either a 
nitrate, an iodate, a chlorate, or a bromate. On 
a little nitre, mixed with copper-filings, I now 

• The most approved hair-dyes consist of a mixture of 
oxide of lead and lime. In order to understand the theory 
of the process, it is only necessary to be informed that the 
hair of animals evolves hydrosulphuric acid gas, which has 
the property of blackening preparations of lead. The use 
of the lime is to remove oily matter, which would defeat 
the object intended. 



CARBONATES — SULPHATES PHOSPHATES. 243 

pour some oil-of-vitriol : — red nitrous fumes are 
immediately liberated ; a salt which makes 
touch-paper, and when mixed with copper- 
filings evolves red fumes on the addition of 
sulphuric acid must be a nitrate. 

Chloric, iodic, and bromic acids unite with 
bases forming chlorates, iodates, and bromates ; 
salts which in many of their properties are very 
similar to nitrates. 

Carbonic acid unites with bases and forms 
salts, which are termed carbonates. They are 
distinguished from other salts by effervescing 
when acted on by acids ; this effervescence 
depending upon the escape of carbonic acid 
gas. Marble and chalk are two different forms 
of carbonate of lime, and white-lead, used in 
painting, is a carbonate of that metal. Many of 
the carbonates occur native, among which I may 
mention carbonates of soda, baryta, strontia, 
lime, magnesia, and of the protoxides of man- 
ganese, iron, copper, and lead. 

Sulphuric acid by combining with bases 
forms sulphates, which may all be prepared 
artificially, but some exist as natural products. 
I may mention sulphate of lime, or plaster of 
Paris ; sulphate of magnesia, or Epsom salt, 
and sulphate of baryta. The test for sulphuric 

r2 



244 MANUFACTURE OF PORCELAIN. 

acid and sulphates is a soluble salt of baryta, 
as I explained to you on a former occasion. — 
{Page 161.) 

Phosphoric acid by combining with bases 
forms phosphates ; phosphate of lime enters 
largely into the formation of bones, and was 
formerly known by the term bone-earth. 

The borates, or combinations of boracic acid 
with bases, are none of them very important if 
we except biborate of soda, commonly called 
borax, a substance much used in medicine and 
the arts. 

Silicic acid combines with bases, and forms 
salts, called silicates, which are a very numer- 
ous and important class of substances. The 
silicates are found very abundantly in nature : 
clay is an active silicate of alumina, and there- 
fore, without any impropriety of chemical lan- 
guage, we may affirm, that the very cups and 
saucers are masses of a salt, and also the brick- 
walls which compose our dwellings. The finest 
porcelain was formerly manufactured in China, 
the necessary mixture of silicic acid and alu- 
mina being obtained by blending together two 
materials, called respectively by the Chinese 
kaolin and petunsi. Without possessing the 
advantage of these substances, other nations 



MANUFACTURE OF PORCELAIN. 245 

have, at length, far outstripped the Chinese 
in this very beautiful manufacture. The mak- 
ing of china-ware is now extensively carried on 
in England, Prussia, and France. Instead of 
using kaolin and petunsi, European nations 
are under the necessity of employing a mix- 
ture of clay and powdered flints, from which 
is obtained a ware of equal, if not superior, 
beauty to that prepared in China ; while the 
excellence of design and colouring are infinitely 
beyond any thing of the kind ever accomplished 
by the Chinese. 

The preparation of earthenware is divided into 
a great many separate operations. In the first 
place, a mass of prepared clay is moulded into 
a shape somewhat like that intended, by the 
hand alone ; afterwards the circular parts are 
turned in a lathe, and the various ornaments, 
such as flowers and leaves in relief, handles, 
and so forth, are cast in moulds and stuck on 
separately. The vessel thus fashioned into its 
requisite form is allowed to dry, when the va- 
rious colours are laid on ;* and it is then baked 
to cause partial fusion : afterwards it has to be 
glazed, which is effected by covering it with a 

* Blues are produced by preparations of cobalt ;— bright 
red and purple by preparations of gold ;— yellow by chro- 
mate of iron, and green by preparations of copper. 



246 MANUFACTURE OF GLASS. 

thin layer of some easily fusible substance, and 
then exposing it to heat again, which causes 
the glaze to melt, and the ware to be covered 
with a thin layer of glass. 

Among the most useful of the artificial com- 
pounds of silicic acid must be mentioned glass, 
of which there are various kinds, differing in 
the nature as well as in the quality and relative 
quantity of their components. Thus we have 
given bottle-glass, window-glass, flint, and 
plate-glass. Green bottle-glass is a silicate of 
soda and iron, made with very impure and 
coarse materials. Window-glass contains less 
iron, and is composed of materials altogether 
more pure. 

Plate-glass contains no iron, and is a silicate 
of soda, almost uncontaminated. Flint-glass is 
a silicate of soda and of oxide of lead, the 
latter substance rendering it exceedingly fusi- 
ble, and, consequently, well adapted for being 
formed or fashioned into different shapes. Win- 
dow-glass is blown into immense bubbles or 
globes, which being cut open whilst in a soft 
condition, and allowed to expand on flat iron 
surfaces, form the flat pieces, or sheets, which we 
see. Plate-glass, however, is not blown but 
cast in large iron frames, and subsequently 
polished; hence it is a far more expensive ma- 



PROCESS OF ANNEALING. 247 

terial. It is necessary that instruments of glass 
should be allowed to cool very gradually, other- 
wise they are subject to fracture from the 
slightest causes ; the external parts quickly 
becoming solid, and acquiring their utmost 
contraction, whilst the internal parts have not 
been enabled to accomplish this, and hence 
they are continually endeavouring to arrange 
themselves differently. To obviate this incon- 
venience, glass, after having been formed into 
any shape, undergoes a process called anneal- 
ing, which consists in passing it gradually 
through a long oven or furnace, one extremity 
of which is very hot and the other quite cool. 
Now, by means of a proper contrivance, the 
glass articles are gradually pushed from the hot 
to the cool extremity, and thus every facility is 
given their particles to contract with equability. 
This process of annealing occupies a time 
more or less extended in proportion to the size 
of the vessels undergoing the operation ; hence 
it is that illegal glass-works, in which the 
operations are carried on by stealth, and the 
process of annealing gone through in a hurry, 
never turn out good and lasting articles : many, 
indeed, appear as perfect and transparent as 
those procured from legal sources, but a slight 



248 CHANGES EFFECTED BY COMBINATION. 

blow, or a little warm water is generally suf- 
ficient for their destruction. 

And now, before concluding this limited 
account of salts, let me direct your attention to 
the wonderful and startling changes effected by 
combination. Who would have imagined that 
Epsom salt contained oil-of-vitriol ; that mark- 
ing-ink contained silver ; that iron, lead, copper, 
and indeed every other metal, might all be ren- 
dered soluble ? Who, I say, would have ima- 
gined them capable of such alteration ? We 
may compare the elements of this globe to 
persons at a masquerade ; we may compare 
them to the fabled metamorphoses of the poets, 
who represented inanimate things changing 
into living forms, and human beings into 
beasts, trees, and stones; in a word, we may 
give wing to fancy, and bid her skim the re- 
gions of romance to find wonders for our ad- 
miration ; yet fancy herself could never have 
invented half the ideal changes of form, which 
chemistry shows us in reality. But although 
bodies are so continually altering their combi- 
nations, and assuming different forms, colours, 
and conditions, yet they are endowed with cer- 
tain properties which never change ; properties 
of which the chemist alone is aware, and the 



METALS RENDERED SOLUBLE. 249 

knowledge of which is a master-key, admitting 
him to the deepest mysteries. 

It requires no great penetration to distinguish 
between a piece of iron and a piece of silver ; 
but if these metals were in the state of solu- 
tion, something more than ordinary experience 
would be absolutely necessary to enable one to 
form an opinion. 

A person unacquainted with chemistry, on 
being shown two solutions each as limped as 
water, would immediately conclude that neither 
of them could by any possibility contain a me- 
tal. Such a person has already formed his 
opinions and associations; when thinking about 
a metal, he brings to his mind the ideas of 
hardness, opacity, and great weight : if told 
that a certain transparent solution contained 
iron, he would probably figure to himself a nail 
immersed in a glass of water, as a self-evident 
means of contradicting the assertion. The 
chemist, on the other hand, does not associate 
with iron the qualities of opacity, hardness, or 
weight, as indispensable to its existence, he 
merely regards them as indispensable to iron in 
an uncombined state. 



250 



LECTURE XIX. 

ANALYTICAL CHEMISTRY TOXICOLOGY, OR THE 

CHEMISTRY OF POISONS. 

The operation by which we are enabled to 
discover the chemical composition of any sub- 
stance is termed analysis, a word which means 
unloosing or pulling to pieces. We are all of 
us, to a certain extent, analytical chemists, 
however unconscious we may be of our power. 
In order to illustrate this position, I will take 
an example ; I will suppose that a piece of 
platinum and a piece of lead are given to a 
person totally ignorant of chemistry, with a 
request that he would distinguish the one from 
the other. Now lead is soft ; platinum is soft 
also ; lead is whitish, so indeed is platinum; it is 
evident that some other distinction is required. 
Our novice would now probably try the effect 
of heating his metals : one melts with great 
facility, the other does not melt at all ; and 
now it is quite evident which metal is lead. 
By proceedings no less rational than this, 



ANALYTICAL CHEMISTRY. 251 

although rather less evident, the chemist per- 
forms his most elaborate analyses, and is able 
to discover, as if by magic, small quantities of 
substances entering into the most complicated 
mixtures : — to demonstrate that a body many 
years buried was a victim to poisoning; — to se- 
parate this poison, and exhibit it in a court of 
justice ; to detect less than the thousandth part 
of a grain of iron, lead, arsenic, or other me- 
tals, although dissolved in a hogshead of water; 
and to arrive at many other conclusions no less 
wonderful and useful. It requires a study of 
many years to make an expert analytical che- 
mist ; but to understand the first principles of 
analysis is not at all difficult. I have before 
me solutions of four different metallic com- 
pounds ; sulphate of iron, sulphate of copper, 
nitrate of silver, and nitrate of lead. We will 
now proceed to test them, so as to distinguish one 
from another. The tests I shall employ are: — • 
A solution of hydrosulphuric acid. 

ferrocyanide of potassium. 

ammonia. 

common salt. 

iodide of potassium. 

I will suppose we have been informed that 
each of the solutions contains a metal, but we 
do not know what the metals are. 



252 ANALYTICAL CHEMISTRY. 

Now solutions of all those metals which form 
with oxygen, alkalies, and earths, are neither 
affected by hydrosulphuric acid nor by ferro- 
cyanide of potassium. 

Solutionsof nearly all the remaining metalsare 
affected either by hydrosulphuric acid,or by fer- 
rocyanide of potassium, and all of them except 
five, namely, uranium, iron, manganese, cobalt, 
and nickel, by hydrosulrjhuric acid alone. 

First, then, I test a little of each liquid with 
hydrosulphuric acid. The silver, lead, and 
copper solutions are blackened, but the iron 
one remains unaltered. Hydrosulphuric acid 
strikes a black colour with many metals, but 
with arsenic and cadmium it produces a yellow, 
and with antimony a red colour ; therefore our 
solutions contain neither of these. 

Now I add to each liquid ferrocyanide of 
potassium, which strikes with the iron solution 
a deep blue, with the copper one a brown, and 
with the silver and lead it yields white preci- 
pitates. No metal except iron yields with this 
substance a blue colour ; therefore we have 
already determined what one solution contains. 

Again, only four metals, copper, uranium, tan- 
talium, and molybdenum, yield a brown colour 
with this test ; the three latter are so rare that, 
for all practical purposes, we may consider it 



ANALYTICAL CHEMISTRY. 



253 



determined that copper is the metal ; however, 
in order to be quite certain, I add to some of the 
questionable liquid a little of the solution of 
ammonia, which affords a blue colour, and proves 
to me that the solution must contain copper. 

To some of the two remaining liquids, very- 
much diluted * I add a solution of common salt; 
when immediately in one glass there fall down 
white curdy flakes, and these are soluble in am- 
monia; which facts, taken conjointly, prove that 
the solution contains silver. To the remain- 
ing liquid I add iodide of potassium, and ob- 
tain a deep yellow precipitate, by which I know 
that lead is present. Salts of silver also afford 
a yellow precipitate with iodide of potassium, 
but a very light yellow. Now we may con- 
struct a table of the colours produced by tests on 
the four metals, iron, silver, lead, and copper. 





Iron 

Solution. 


Silver 

Solution. 


Lead 
Solution. 


Copper 
Solution. 

black. 


Hydrosulphuric acid 


_ 


black 


black 


Ferrocyanide of potassium 


blue 


white 


white 


brown. 


Chloride of sodium 


- 


white 


none in weak 
solutions 


- 


Iodide of potassium 


- 


light yellow 


deep yellow 


- 



* Chloride of sodium will throw down or precipitate with 
solutions of silver salts, however much they may be diluted ; 
but only with strong solutions of salts of lead. 



254 ANALYTICAL CHEMISTRY. 

We have hitherto merely ascertained what 
metal each of the four solutions contains ; but 
metals, I have before remarked, are not soluble 
except in combination, and consequently our 
information respecting the solutions is not yet 
complete. I now proceed to test each of the 
four solutions for substances which enable the 
metals to be dissolved. First, then, I add to the 
iron and copper solutions a few drops of a so- 
lution of hydrochlorate of baryta, and imme- 
diately you observe there falls a copious white 
precipitate, which I find is quite insoluble in 
boiling nitric acid;* in fact it is sulphate of 
baryta, and hence I know that each of the 
two solutions contained sulphuric acid. One 
consisted of sulphate of oxide of iron, and the 
other of sulphate of oxide of copper. 

Again, I find that the silver and lead solu- 
tions do not afford a precipitate with hydro- 
chlorate of baryta, and this fact supplies me with 
the negative information that neither of them 
contains sulphuric acid. I find, however, that 
by dipping a piece of paper into either of these 
solutions I convert it into touch-paper, and 
from this fact I learn that they must contain 
either nitric, iodic, bromic, or chloric acid.t 
* 1'age 161. + Page 242. 



ANALYTICAL CHEMISTRY. 255 

For all practical purposes the question is 
already settled ; — as the three latter acids are 
very rare indeed ; but in order to be quite cer- 
tain I evaporate a little of each solution to 
dryness, and add to the residue, mixed with 
filings of copper, a small quantity of sulphuric 
acid ; immediately there appear red fumes of 
binoxide of nitrogen, which could only have 
been liberated from nitric acid, {see p. 243,) 
therefore one solution contained nitrate of ox- 
ide of lead, and the other nitrate of oxide of 
copper. 

The operation which we have just been per- 
forming is called testing, and consists merely 
in ascertaining the nature of ingredients enter- 
ing into a mixture, without endeavouring to se- 
parate them, or to discover their relative pro- 
portions. It is quite possible, by means of a 
series of operations, rather more complicated 
than those which I have been describing, to 
separate the acids from the metallic oxides, and 
even to separate the metals from oxygen ; but 
as I am only giving a faint outline of analytical 
chemistry to young beginners, I shall content 
myself with showing how metallic silver may 
be separated and obtained in a pure state. Into 
the silver solution I immerse a clean slip of 
copper, and a few seconds having elapsed, you 



256 TOXICOLOGY. 

observe that the silver has been deposited in 
the form of bright metallic scales. There are 
several other means of accomplishing the same 
result, but this is the easiest to be put into exe- 
cution. 

That branch of analytical chemistry which 
relates to the discovery of poisons and the 
treatment of poisoning, is called toxicology 
from toxon a bow ; the term evidently convey- 
ing an allusion to poisoned arrows. The 
science of toxicology has lately been brought 
to an amazing degree of perfection, and, at the 
present time, is cultivated by some of the most 
celebrated chemists. Formerly, if a person 
should by chance have the misfortune to swal- 
low poison, he was treated altogether at ran- 
dom ; the usual remedy was soap-suds, which, 
indeed, in some cases of poisoning is really 
beneficial ; in others is of no use whatever. 
We now act on more philosophic principles, 
and in the majority of cases death is prevented 
by a timely interposition of art. 

Poisons may be divided into those which 
exert a mechanical, and those which exert a 
chemical agency : for instance, a quantity of 
broken glass if swallowed will kill by lacerating 
the coats of the stomach ; this is a mechanical 
agency. Oil-of-vitriol, aquafortis, and spirit-of- 



TOXICOLOGY. 257 

salt (the sulphuric, nitric, and hydrochloric 
acids) act by setting up violent inflammation, 
and perforating the stomach ; these are chemi- 
cal poisons. One of the greatest wonders in 
chemistry is the entire change which certain 
substances undergo by combination. Sulphuric 
acid, or oil-of-vitriol is a deadly poison. Epsom 
salt, or sulphate of magnesia, a body which 
contains sulphuric acid, is quite harmless. If, 
then, a person had inadvertently swallowed 
sulphuric acid, would not common sense prompt 
a chemist to administer magnesia, with which 
the acid might combine, and form Epsom salt ? 
This, indeed, is the most suitable plan of treat- 
ment that can be followed. But how is the 
magnesia to be administered ? it cannot be 
given in the form of dry powder ; nor mixed 
with water, for water and sulphuric acid when 
they come in contact with each other develope 
a high degree of heat : mix the magnesia with 
milk, and even with a very small quantity of 
this fluid. 

Chemical action takes place with the greatest 
facility, when the agents are in a state of solu- 
tion ; therefore the rapidity of action possessed 
by a chemical poison is in the ratio of its solu- 
bility : if by any means we can render it in- 

s 



258 TOXICOLOGY. 

soluble, then it ceases to be a poisonous agent. 
All the soluble compounds of the alkaline earth 
baryta, and, indeed, any solutions containing 
the metal barium are violent poisons — but 
baryta and sulphuric acid form a compound 
which is quite insoluble, and hence, quite 
harmless. If, then, a person had taken a salt 
of baryta, or, indeed, any solution of barium, 
theory requires the administration of sulphuric 
acid ; but this substance itself is a poison, there- 
fore a dose too much would obviate all our good 
intentions ; besides, it would burn the throat 
before arriving at its destination, the stomach ; 
what, then, is to be done ? We must adminis- 
ter some compound which contains sulphuric 
acid in a harmless form, and none is more gene- 
rally available than Epsom salt. This substance 
is also an antidote for preparations of lead.* 

Again, a person may have swallowed oxalic 
acid, which in a few minutes will certainly kill 
him, if remedies be not at hand. Oxalic acid 
when combined with lime is inert ; but lime, 
too, is a poison : give, then, some form of car- 
bonate of lime : run to the kitchen for some 
whiting; get a lump of chalk ; or if neither be at 
hand, quickly knock down a piece of the wall, 
• Because sulphate of lead is insoluble. 



TOXICOLOGY. 259 

and administer it mixed with milk or water ; 
do this immediately, and the individual is cer- 
tainly saved ; but wait a few minutes, and he 
as certainly dies ! 

A person may have been poisoned with pre- 
parations of copper, or of mercury ; generally the 
bichloride or corrosive sublimate; what then 
is to be done ? Give the white of eggs beat 
up with water, immediately, and the patient is 
secure. These are a few examples of the tri- 
umphs of chemistry, and it is much to be regret- 
ted that antidotes still remain to be discovered 
for a considerable number of poisons, the ill 
effects from which can only be prevented by 
removing them from the stomach, either by 
emetics or the stomach-pump. 

There is not yet discovered any satisfactory 
antidote for white arsenic, (arsenious acid,) 
cases of poisoning from which are of such fre- 
quent occurrence ; but even in this instance it is 
very proper to administer white of egg, which 
does not effect any chemical change on the 
poison, it is true, but yet acts beneficially, by 
sheathing the stomach. 

I promised that I would show you the tests 
for white arsenic, and how to separate it from a 
solution, which I shall now proceed to do. 

s2 



2G0 TOXICOLOGY. 

Into one glass containing a solution of this 
poison I throw some lime-water, and a white 
precipitate falls. Into the second glass of solu- 
tion I let fall two or three drops of a solution 
of nitrate of silver, and a single drop of harts- 
horn, (solution of ammonia,) when a yellow pre- 
cipitate falls: into the third glass I pour a 
small quantity of solution of sulphate of copper, 
together with a drop of hartshorn ; a green 
precipitate falls: and through the solution con- 
tained in the fourth glass I pass a stream of 
hydrosulphuric acid gas, which throws down a 
yellow precipitate; orpiment,or sesqui-sulphuret 
of arsenicum. Nothing besides arsenious acid 
would have afforded the same appearances with 
the same tests, i" could have sworn that the 
solution contained arsenious acid from the ap- 
pearances elicited by the foregoing tests ; but 
in a court of justice further information is ne- 
cessary : the poison itself must be produced. 

There are two methods of effecting this, but 
I shall only mention one. Either of the four 
precipitates just produced is to be mixed with 
a substance called black flux,* and exposed to 

* Black flux is composed of pure carbonate of potash and 
charcoal, made by throwing into a red-hot crucible a mix- 
ture of nitre and cream-of-tartar. 



TOXICOLOGY. 



261 



heat in a glass tube, when shining metallic 
arsenicum arises and lines the tube with a grey 
crust. This crust of arsenicum, if again heated, 
absorbs oxygen, and forms white arsenic, the 
poison, which deposits in little crystals. The 
process of obtaining metallic arsenicum from a 
precipitate is termed the reduction test. All 
the various tests here described may be advan- 
tageously condensed into a tabular form. 

TESTS FOR ARSENIOTJS ACID, OR WHITE 
ARSENIC. 



Lime-water. 


Ammoniacal 
Nitrate 
of Silver. 


Ammoniacal 
Sulphate 
of Copper. 


Hydrosulphuric 
Acid. 


Reduction 
Test. 


White. 


Yellow. 


Green. 


Yellow 


Metallic 

coat of 

Arsenicum. 



For opium, henbane, nux-vomica, and, in- 
deed, the majority of poisons derived from the 
vegetable and animal creations, there exist no 
satisfactory antidotes. This remark equally 
applies to hydrocyanic, or prussic acid. 

In discussing the subject of toxicology I may 
have gone into many dry and tiresome details ; 
but the importance of this branch of chemistry 
demands our most especial attention. Opera- 
tions connected with some sciences need only 
be remembered in their general principles ; the 



262 TOXICOLOGY. 

particularsbeing ascertained when convenientby 
reference to books, — the delay of a few minutes, 
hours, or perhaps days not proving of the least 
consequence ; but all that department of toxi- 
cology which relates to the administration of 
antidotes should be impressed on your memories, 
firmly as the letters of the alphabet : the appli- 
cation of your knowledge this minute may save 
the life of a fellow-being ; the next may be too 
late. 

In order that the antidotes for poisons may 
be easily remembered, 1 here present them in a 
tabular form. 

POISONS. ANTIDOTES. 

C Magnesia (calcined) or Carbonate 
Sulphuric Acid I „f Magnesia, or some form of 

•k'' nc "\ Carbonate of Lime, as whiting, 

Hydrochloric 1 cha i tj administered in milk. 

Any form of Carbonate of Lime, 
Oxalic Acid. | mixed with milk or water _ 

/None. Administer thirty grains of 
white vitriol (Sulphate of Zinc) as 
an emetic,* tickling the back part 
of the mouth and throat with a 
feather to promote its action ; 
I give also white of eggs, beat up 
\ with milk or water. See p. 259. 

• A very efficient emetic is a tea-spoonful of mustard ad- 
ministered in a cup of warm water ; it has, moreover, the 
additional advantage of being generally at hand. 



White Arsenic. 



TOXICOLOGY. 



263 



POISONS. 
Preparations of 
Copper and Mer- 
cury. 
Preparations of tbe^ 
metal Barium 
and its oxide Ba- 
ryta. Prepara- 1 
tions of Lead. 



Opium. 



ANTIDOTES. 

White of egg beat up with milk 
or water. 



Epsom Salt. 



/ No antidote on which any reliance 
can be placed : administer thirty 
grains of white vitriol, tickle the 
back part of the mouth and throat 
with a feather. Do not give vine- 
gar ;* neither must you allow 
the patient to sleep. Keep him 
awake by every possible means : 
make him walk up and down a 
yard between two men : if he 
then sleep, push a needle or a pin 
under his nail to the quick, and 
dash cold water over his head. 



V 



* This was formerly recommended ; but there cannot 
be a worse practice. The active principle of opium is mor- 
phia,— an alkali :— the solubility, and consequent activity of 
which is much increased by combination with acids. 



264 



LECTURE XX. 

REMARKS ON GRAVITATION, COHESION, AND AF- 
FINITY SINGLE AND DOUBLE ELECTIVE AF- 
FINITY — SINGLE AND DOUBLE DECOMPOSITION. 

Having now gone through that portion of che- 
mistry which relates to beings without life, I 
purpose introducing you to another department 
of the science ; to organic chemistry, or the 
chemistry of living beings. But previous to 
our entering upon this wide and very interest- 
ing field it will be advantageous for us to take 
a retrospective view of the regions we have 
already traversed. Anxious to avoid burden- 
ing your memory with more than was absolutely 
necessary, and to refrain from announcing laws 
and properties before you had been made ac- 
quainted with instances of their operation, I 
have not said much respecting the attraction to 
which all material things are subject. There 
are usually mentioned three kinds of attraction, 
gravitation, cohesion, and chemical attraction 



GRAVITATION. 265 

or affinity. To the former I have already made 
allusion, and to a certain extent explained it ; 
but the very great importance of this attraction 
demands that we should pay it still further at- 
tention. Gravitation may be defined to be the 
force which causes bodies to approach each 
other's centres : acting in straight lines at sensi- 
ble and often very great distances, and decreas- 
ing in power as the square of the distance in- 
creases ; * this distance being calculated from 
the centres of gravitating masses. I have al- 
ready proved t that all bodies owe their weight 
to the operation of this force. 

I have mentioned that the farther bodies are 
removed from the centre of the earth, or point 
of terrestrial gravitation, the less does their 
weight become ; and I have contented myself 
with referring the decreased weight of bodies 
at the equator to the fact of their increased dis- 
tance from the centre alone. But this expla- 
nation is only partial ; we must seek for some 
anterior cause : we must account for this in- 
creased distance, and show why the equatorial 
diameter of the earth exceeds the polar. 

* A square in arithmetic is any number multiplied by it- 
self: — thus 4 is the square of 2, and 9 of 3. 
+ Page 25. 



266 ATTRACTION OF GRAVITATION. 

The shape of this planet when first created is 
supposed to have been a sphere ;* which sup- 
position granted, every point on its surface 
must have been equidistant from the centre, and 
the power or force of gravitation must have been 
the same whether at the equator or at the poles. 
But the earth was caused to whirl round on an 
axis with great rapidity, t by the agency of ano- 
ther force, termed the centrifugal, and in con- 
sequence of which all the particles of the earth, 
except such as might be situated in the geo- 
metrical axis of rotation, were disturbed, and 
driven by main force towards some part of the 
circumference of the planet. Those particles 
which were situated farthest from the geometric 

" Of course no account is taken of its various hills and 
mountains, the general figure of the earth being no more 
interfered with by such little excrescences than is the figure 
of a billiard-ball altered by little particles of dust which ad- 
here to its surface. 

+ This is the diurnal motion of the earth ; the cause of 
day and night. Its rate of velocity differs for different 
parallels of latitude, the inhabitants of the equator being 
carried by this motion 1042 miles every hour, and those 
under the parallel of London about 644 miles in the same 
space of time. Besides this diurnal motion, which alone has 
connexion with terrestrial weight, the earth and its inha- 
bitants are subject to another, the annual motion, or rotation 
round the sun ; this is at the rate of more than 68,000 miles 
per hour, and is participated equally by every inhabitant on 
the globe, whereas the diurnal motion is not. 



CENTRIFUGAL FORCE. 267 

axis were of course most subject to the influ- 
ence of the centrifugal force, or, in other words, 
were caused to move faster, and consequently 
were driven farthest away. Therefore it ap- 
pears that the cause why bodies at the equator 
weigh less than at the poles is ultimately re- 
ferrible to the increased equatorial motion, pro- 
duced by an increase of the centrifugal force, 
which has caused the earth to assume its present 
oblate spheroidal shape, and immediately or 
proximately referrible to the increased equa- 
torial diameter thus produced. 

The agency of a centrifugal force may be 
very simply illustrated by an experiment. If a 
perfect globe or sphere of any soft and readily- 
yielding substance, such as clay, be perforated 
through the centre by a stick, and if by means 
of this stick as a handle or axis, it be made to 
revolve rapidly, its globular form will be de- 
stroyed ; and becoming flattened around the 
two points which are perforated by the stick, it 
will everywhere else bulge out in such a man- 
ner that the diameter, which is traversed by 
the stick, will be shorter than any other: that 
diameter which is at right-angles to the stick, 
or which lies directly across it, being the 
longest. 



268 ATTRACTION OF COHESION. 

The attraction of cohesion is altogether dif- 
ferent from gravitation, and, as the term in- 
dicates, it means a sticking together. I take 
a piece of marble, and having lifted it from the 
ground, I let it fall. By the agency of gravita- 
tion it is brought to the ground, and on account 
of the sudden shock it breaks in pieces, be- 
cause its attraction of cohesion has been over- 
come. Cohesion, then, was the attractive force 
which kept the particles of marble in contact 
with each other, and this attraction being over- 
come, the particles separated. However near 
I approximate these pieces of marble together, 
I cannot make them approach so near as is 
requisite for bringing them within the sphere 
of each other's cohesive attraction, and for 
causing them to join again into a mass ; there- 
fore cohesion is said to exert its force at in- 
sensible distances, as they are far too small to 
be appreciated or taken cognizance of by the 
senses. 

I may overcome the marble's cohesion by 
pulverization, or pounding, to a still greater ex- 
tent ; but even if I reduce it to the condition 
of a most impalpable powder, I cannot convert 
it into any thing but marble, although it is 
made up of two substances, carbonic acid and 



CHEMICAL ATTRACTION, OR AFFINITY. 269 

lime, which must be held together by some 
force quite independent of cohesion ; seeing 
that the destruction of the latter does not en- 
able them to be separated from each other. 

To sum up, then, all that we have demon- 
strated respecting cohesion, it may be defined 
as that attractive force which, acting at insen- 
sible distances between particles of similar na- 
tures, keeps them firmly together; in the in- 
stance just cited, it joins two particles of car- 
bonate of lime together, but not a particle of 
carbonic acid to another of lime in order to 
form the carbonate ; this being effected by 
another force, named chemical attraction or 
affinity. 

The marble falling on the ground breaks into 
pieces, and a fragment is thrown into a dish of 
sulphuric acid; effervescence immediately takes 
place, from the escape of carbonic acid, and a 
total change of composition ensues ; the sul- 
phuric acid uniting with lime, in order to form 
sulphate of lime, or plaster of Paris. This acid 
is just as securely attached to the lime as the 
particles of marble or carbonate of lime were 
attached to each other; not, however, by cohe- 
sion, but by chemical attraction or affinity. 



270 ELECTIVE AFFINITY. 

It appears that sulphuric acid and lime possess 
a greater tendency for uniting with each other 
than carbonic acid and lime ; or, to speak figura- 
tively, lime selects or elects the sulphuric acid, 
by preference, hence this is an instance of elec- 
tive affinity. As only one compound (sulphate 
of lime) is formed, the elective affinity is said 
to be single, and single decomposition is said 
to have occurred ; but if two compounds had 
been formed, then we should have had an in- 
stance of double elective affinity, and double 
decomposition ; as an example of the latter, I 
mix nitrate of baryta with sulphate of soda, 
when, owing to an interchange of elements, 
there result two compounds, nitrate of soda 
and sulphate of baryta.* 

* For instances of single and double elective affinity 
effecting single and double decomposition, see page 167. 



271 



LECTURE XXI. 

INTRODUCTION TO ORGANIC CHEMISTRY DIF- 
FERENCES EXISTING BETWEEN THE STRUC- 
TURE OF ORGANIZED AND INORGANIZED 

BODIES DIFFERENCE BETWEEN ANIMALS AND 

VEGETABLES PROXIMATE VEGETABLE PRIN- 
CIPLES. 

Although it may be difficult, nay impossible, 
to offer a correct definition of the nature of 
life, I presume there are none of my young 
friends who will not perfectly comprehend me, 
when I inform them that things are divided 
into some which possess life, and others 
which do not. But nature has thought pro- 
per to withhold life from such bodies as are 
merely formed by the agency of those grand 
forces which regulate the inanimate portion of 
the universe. It has been decreed that life 
shall be associated with a peculiar and elabo- 
rate structure. Animals have parts adapted for 
touch, sight, taste, and smell ; while structures 
for the circulation of blood, or sap, are common 



272 ORGANIC CHEMISTRY. 

to both animals and vegetables. These parts 
or structures are called organs ; hence arises 
the very natural distinction between organic 
and inorganic bodies, and hence the terms or- 
ganic and inorganic chemistry. 

So little do organized and inorganized things 
resemble each other, that a person unacquainted 
with chemistry would imagine them to be com- 
posed of elements altogether different, but such 
is not the case. The great Author of nature 
has confined himself in the formation of living 
beings to the use of a very few materials. 
Vegetables are chiefly composed of carbon, 
hydrogen, and oxygen ; animals of carbon, 
hydrogen, oxygen, and nitrogen. This rule, 
however, is not universal, for there are some 
animal substances without nitrogen, and some 
vegetable ones with it ; yet the distinctive cha- 
racter of animal matters in general consists in 
the presence of nitrogen. But we are not to 
regard these elements as the owfyoneswhich con- 
tribute to the formation of living or organized 
beings ; vegetables have entering into their 
composition a great many different metals. 
Potassium and sodium enter so abundantly 
into the composition of land and sea plants, 
that we cannot but regard those metals as ne- 



FLINTY MATTER IN CANE AND STRAW. 273 

cessary constituents of the vegetable king- 
dom. 

The blood of animals contains iron; — and cal- 
cium, the metal of lime, exists largely in bones, 
combined with oxygen and phosphorus, as 
phosphate of lime. Other metals still more 
uncommon have been affirmed to exist in cer- 
tain vegetables. Coffee and tobacco are both 
of them said to yield traces of copper, and 
gold is reputed to have been discovered in 
tamarinds. Certain productions of the vege- 
table kingdom are incrusted with a coating of 
silicic acid, or flint: the shining surface of bam- 
boo is composed of nothing but flint, and so like- 
wise is the external glossy part of a straw. Two 
pieces of bamboo may even be made to yield 
sparks by striking them together; and an expert 
manipulator with the blow-pipe, will melt the 
flinty and alkaline matters of a common wheaten 
straw into a transparent bead of glass. 

It was once imagined that the elements of 
organized and those of inorganized beings were 
united by forces altogether different, and that 
the ordinary chemical powers, as evinced by 
inorganic bodies, gave way in the formation of 
animals and vegetables to other forces of a dif- 
ferent kind. 

T 



274 ORGANIC CHEMISTRY. 

Since the science of chemistry has become 
more perfect, it is now known that the ordinary 
forces which determine the composition of in- 
organic things are also active in animals and 
vegetables, but their agency is very much mo- 
dified by the principle of life ; which does not 
supersede inorganic forces, but is merely super- 
added to them. 

As all organized beings are either animals or 
vegetables, so the most natural division of this 
part of our science will necessarily be into ani- 
mal and vegetable chemistry ; a division, how- 
ever, which participates in the imperfections of 
every other human invention, as will be here- 
after perceived. We do not find it at all times 
an easy matter to decide whether an organized 
being belongs to the animal or vegetable world. 
It is easy enough to distinguish between an oak- 
tree and an elephant, and to determine that each 
belongs to a different organic kingdom; but it is 
not quite so easy to ascertain the relative position 
in creation of a sea-weed and a sponge : the 
latter is now universally allowed to belong to the 
animal creation, although apparently but little 
or nothing removed from the former, which is 
regarded in the light of a vegetable. As the 
precise line of boundary, then, between the ani- 



SUGAR, STARCH, GUM. 275 

mal and the vegetable world is still undefined, 
so must a division of organic chemistry into 
animal and vegetable be imperfect : neverthe- 
less, it is useful, and still very generally fol- 
lowed. 

One of the first subjects of wonder encoun- 
tered by a person just entering upon the study 
of organic chemistry, is, that so many substances^ 
of natures the most opposite, could ever have 
been made out of the same materials. What 
substances can be more apparently different 
than sugar, starch, and gum ? Yet each is 
composed of three elements, carbon, hydrogen, 
and oxygen. This similarity of composition 
which exists between substances in the organic 
kingdom, enables us very often to change one 
into another. For instance, it is well known 
that a solution of sugar in water if exposed to 
the air at a certain temperature becomes vine- 
gar, a change which is easily intelligible to a 
person who knows that they are both composed 
of the same elements united in different pro- 
portions. 

Although we may sometimes effect changes 
on organic principles, as, for instance, in the 
case of sugar, yet we can in no instance make 
them by an artificial admixture of their ele- 

t 2 



276 CLASSIFICATION OF ORGANIC BODIES. 

ments. Neither sugar, starch, nor gum can he 
made artificially by any combination whatsoever 
of hydrogen, oxygen, and carbon ; these ele- 
ments can only be joined in the requisite man- 
ner by the agency of life, and in this lies the 
great distinction between organic and inorganic 
bodies. 

The chemistry of inorganic substances is so 
well known, that we classify them in a scien- 
tific manner ; that is to say, according to their 
chemical composition ; but it is only within 
the last few years that the same precision has 
been introduced into the department of organic 
chemistry. Formerly animal and vegetable 
principles were classified according to their 
external propeties ; for instance, under the 
heads of oils, acids, alkalies, and neutral bodies: 
lately, a far more correct method of classi- 
fying them has been introduced, founded on 
their chemical composition ; however, it is far 
too elaborate for our purposes. 

Compound bodies may be regarded under 
two points of view ; with reference to their 
ultimate and to their proximate composition. 
This remark applies to every variety of com- 
pound, whether inorganic or organic, but more 
particularly to the latter. I can take a portion 



PROXIMATE AND ULTIMATE COMPOSITION. 277 

of some plant, and resolve or decompose it into 
carbon, hydrogen, and oxygen, by which means 
I arrive at its ultimate composition, for carbon, 
hydrogen, and oxygen, being ultimate elements, 
cannot be further decomposed. Again, without 
carrying the decomposition so far, I can resolve 
the same vegetable parts into a few substances 
called proximate, such as woody fibre, sugar, 
starch, and gum ; all of which are composed of 
carbon, hydrogen, and oxygen united in various 
proportions. 

These proximate principles of vegetables I 
purpose saying something about, and yet not 
much, for I cannot conceal the fact that organic 
chemistry is one of the most difficult branches of 
the science, and before a person can be even 
moderately acquainted with it he must spend 
many years in its patient and unremitting 
study. 

The proximate principles of vegetables may 
be divided into acids, alkalies, and those which 
are neither acid nor alkaline, and hence are 
termed neutrals. As a matter of convenience I 
shall describe the latter class first, and com- 
mence my description with the proximate prin- 
ciple termed lignin. This very learned term, 
lignin, only means woody fibre, and if any of 



278 LIGNIN, OR WOODY FIBRE. 

my audience wish to see a specimen of this 
proximate principle, let them direct their eyes 
to the first piece of wood in the neighbour- 
hood ; or a purer specimen is afforded by a 
piece of linen. Although the wood of different 
vegetables appears so unlike in its nature, yet 
it is actually made up of the same chemical 
principle. In hard woods the lignin is very 
brittle, while in the form of hemp and flax it is 
so extremely tough and tenacious that it serves 
the purposes of making cordage and linen : dif- 
ferent degrees of toughness and strength are 
not produced by any chemical difference of 
composition. This point being discussed, a 
person commencing the study of chemistry 
stumbles on another, and apparently a more 
valid objection ; that different kinds of woods 
are possessed of different tastes, smells, and ap- 
pearances ; all this is true, but still, chemically 
speaking, there is only one kind of lignin, or 
woody fibre, which, serving as a receptacle for 
any substance that it may be the nature of the 
plant to secrete, must necessarily afford various 
appearances, tastes, and smells. The different 
kinds of firs secrete turpentine, which in a 
manner is absorbed by the woody tissue, and 
deposited between its fibres : hence deal-wood 



LIGNIN GUM. 279 

has the odour of turpentine, although the che- 
mical composition of its lignin is similar to that 
entering into the composition of every other 
tree. All trees of this climate, and, indeed, 
the greater number in all climates, consist of 
wood possessing two different degrees of hard- 
ness, called, respectively, by carpenters, heart- 
wood and sap-wood, and by the scientific 
botanist duramen and alburnum. These two 
kinds of wood may be very nicely observed in 
a lignum-vitae ruler, the light coloured portion 
of which is alburnum and the dark portion du- 
ramen. Both portions are made up of woody 
fibre, but the dark part, or duramen, is satu- 
rated with a substance called guiacum, a secre- 
tion of the plant. This guiacum is not of so 
permeating a nature as turpentine, and hence it 
is almost entirely deposited in the heart-wood, 
while turpentine pervades every part of the 
trunk. 

Another very important proximate vegetable 
principle is gum, of which there are many 
varieties, differing considerably in the ratio of 
their chemical elements, and obtained from a 
great number of different plants. Gum Arabic is 
procured from various species of the acacia, rnore 
particularly the Acacia Arabica, A. Nilotica, 
and A. Seyal. Gum Senegal very nearly corres- 



280 VARIETIES IN STARCH. 

ponds in nature and composition to gum Arabic, 
it is chiefly obtained from the Acacia verek. 
There are also plum and cherry-tree gums, both 
nearly, although not quite, similar in composition 
to gum Arabic. Gum tragacanth is yielded by 
the Astragalus vents, and differs from gum Arabic 
in not being soluble in water, but merely swel- 
ling up and forming a tremulous jelly. 

Starch is a proximate chemical principle, 
very nearly allied in composition to gum, but if 
examined by the microscope, it is found to be 
much more highly organized than the former 
substance, consisting of little vesicles, or bags, 
inclosing a peculiar matter, to which has been 
applied the term amy dine. Starch exists in 
many parts of different vegetables, more especi- 
ally in the seeds of grasses,* and the tubers, 
roots, and trunks of certain other plants. Starch 
which we find employedby the laundressis chiefly 
obtained from wheat, but sometimes from pota- 
toes : naturally it is colourless ; but for certain 
purposes it is tinged blue by means of indigo. 
Arrow-root, tapioca, sago, and cassava are all 
varieties of starch, the uses of which are so well 
known that it is quite unnecessary for me to ex- 
patiate on them here. Arrow- rootis obtained from 

• The term grass is here used in a botanical sense, in- 
cluding wheat, barley, oats, rice, and, indeed, all other grain. 



FORMATION OF SUGAR. 281 

the Maranta arundinacea, and detives its name 
from the circumstance that the expressed juice of 
the plant is useful in curing poisoned wounds. 
Tapioca and cassava are procured from the root 
of the Jatropha manihot, a most poisonous 
plant, and which in its natural state would cer- 
tainly cause death, even if swallowed in very 
small quantities, but the virulent principle is 
destroyed by roasting, and the nutritive sub- 
stances, cassava and tapioca, remain. Sago is 
obtained from the trunk of the Sag us farinifera 
and Phoenix farinifera, both species of palms. 
I have already mentioned that iodine and starch 
are respectively tests for each other, indeed, 
you have seen the experiment performed.* One 
of the most curious properties of starch is the 
facility with which it is converted into sugar 
by the operation of various causes. If I 
expose a solution of starch in water to the 
free access of air for a considerable time, I 
shall ultimately find that there has been gene- 
rated a certain quantity of sugar. If I boil a 
similar solution of starch with a little sul- 
phuric acid, this process is much facilitated, 
and the formation of sugar is more complete. 
The operation of forming sugar from starch 
by artificial means is one of some difficulty : 
• Page 73. 



282 GLUTEN HOW PREPARED. 

nature, however, accomplishes the process with 
far greater ease, as is exemplified in the instance 
of germination, concerning which I shall speak 
hereafter. 

The proximate vegetable principle, sugar, 
exists naturally in a great many vegetables, but 
for commercial purposes it is chiefly obtained 
from the sugar-cane. By artificial means sugar 
may be entirely freed from colouring matter, 
and when crystallized in this condition it be- 
comes what is called white sugar-candy. 

Of sugar there are many varieties, besides 
that which is derived from the canes and other 
kinds of analogous composition; there is sugar 
of grapes, sugar of manna, called mannite, 
sugar of liquorice, called glycirrhizine, and 
sugar of milk. 

Gluten is another important vegetable prin- 
ciple, which exists largely in various kinds of 
grain, particularly wheat. Gluten can easily 
be prepared by the following process : take 
some wheaten dough and expose it to the ac- 
tion of a running stream of cold water, knead- 
ing it well all the time ; by this process, starch 
is washed away, and gluten remains, mixed, 
however, with another principle, termed vege- 
table albumen. Gluten is an exceedingly nu- 
tritive substance, and its prevalence in wheat 



BREAD HOW MADE. 283 

accounts for the superiority of that grain as an 
article of food. It is gluten which imparts 
tenacity to paste, and enables bread to acquire 
its porosity. 

Bread is made by mixing together flour, 
water, and yeast, and afterwards baking ; the 
yeast causes the gluten to ferment, during 
which process carbonic acid, and alcoholic 
vapour are given off, which force their way 
through the mass of dough, and blow it full of 
little bubbles. It appears, then, that the im- 
mediate cause of the porosity or lightness of 
bread is the passage of gas through the sub- 
stance of the dough. Carbonic acid gas is the 
usual agent, but not the only one- Some- 
times confectioners are in the habit of mixing 
with the dough, for making very light pastry, 
sesqui-carbonate of ammonia, (smelling-salts) 
which substance, by the heat employed in bak- 
ing, is either decomposed or driven off in vapour, 
puffing up the dough into a light spongy mass. 

Such are the chief neutral vegetable princi- 
ples ; many others might be enumerated, but I 
do not think it worth while. Let us now turn 
our attention to a few of the vegetable alkalies. 
You remember my mentioning the alkalies am- 
monia, potash, soda, and lithia; these, not 
many years since, were the only ones of which 



284 VEGETABLE ALKALIES. 

chemists had any knowledge ; but as the pro- 
gress of discovery advanced, a class of alkalies 
altogether new dawned from the vegetable 
world. Some little period of time elapsed be- 
fore their claim to be termed alkalies was 
admitted, and they were known by the cautious 
appellation of alkaloids, that is to say, sub- 
stances allied, or similar to alkalies : their alka- 
line claim is now, however, universally recog- 
nized. Few chemical discoveries have con- 
ferred so much benefit upon the practice of 
medicine, as that of the vegetable alkalies. 
Cinchona-bark has been employed for the pur- 
pose of curing agues ever since the commence- 
ment of the seventeenth century : but in order 
to prove of service, this drug must be given in 
doses which are so large that they often produce 
great sickness, and other unpleasant effects. 
Now the activity of cinchona-bark* is concen- 
trated in the alkalies quina cinchonia and ari- 
cina, all the rest being inert matter, and offend- 
ing the stomach. Chemistry has taught us how 
to separate these alkalies, and to give them 
apart from inert woody matter, by which means 
their administration is much more easily ac- 

* Peruvian or cinchona-bark was introduced into Spain 
by Count Cinchon, A.D. 1632. Sometimes it is called 
Jesuits' bark, because the Jesuits strenuously advocated its 



VEGETABLE ACIDS. 285 

cornplished, and their action rendered far more 
effective. Again, that very valuable drug, 
opium, derives its beneficial qualities entirely 
or almost entirely, from an alkali called morphia, 
which chemistry has taught us how to extract, 
and to administer in several advantageous forms. 
The vegetable acids are exceedingly numer- 
ous, and some of them are very important sub- 
stances. The best known and most useful are 
acetic acid, which, when diluted and mixed with 
various impurities constitutes vinegar ; citric 
acid, which exists in lemons, and imparts to them 
their sour taste ; tartaric acid, which is obtained 
from the bitartrate of potash, or cream-of-tartar, 
a substance that deposits in wine-casks ; and 
oxalic acid, which is found in many vegetables, 
particularly in the wood-sorrel, {Oxalis aceto- 
sella,) combined with potash in the form of 
binoxalate of that akali. The substance pur- 
chased in the shops under the name of salt-of- 
lemons, is in reality binoxalate of potash, and is 
much employed for removing ink-stains from 
linen. Oxalic acid is used by chemists as a test 
for lime ; for this purpose either a solution of the 
uncombined acid may be employed, or some of 
its combinations with potash or ammonia ; oxa- 
late of ammonia is generally preferred. With lime 
it throws down a copious and very insoluble 



■286 FIXED AND VOLATILE OILS. 

white precipitate, and hence the efficiency of 
carbonate of lime, (chalk,) as an antidote for 
this poison. Besides the vegetable acids al- 
ready enumerated, there are many others which 
I shall pass over, as they are not very well 
known, neither are they applied to any very 
useful purposes. 

A very large and important class of sub- 
stances derived from both the vegetable and 
animal kingdom, are the oils ; usually consi- 
dered to be neutral bodies, yet they seem to 
possess the properties of acids, at least, the 
greater number of them : oils are divided into 
fixed and volatile, or expressed and essential. 
If I drop a little almond-oil upon a piece of 
paper, and attempt to remove the stain by 
holding it before the fire, my endeavours will be 
fruitless, because almond-oil is a fixed oil, and 
will not readily evaporate ; but if I hold before 
the fire a piece of paper soiled with otto, or oil- 
of-roses, oil-of-lavender, of turpentine, of lemons, 
of peppermint, of cinnamon, of carraways, and 
many others, the stain will speedily disappear, 
the oil flying off in very pungent vapours ; hence 
the latter are termed volatile oils, or sometimes 
essential oils, from their property of readily 
dissolving in spirit, and forming liquids, called 
essences. It is owing to the presence of essen- 



VOLATILE OILS. 287 

tial oils that plants derive their various odours, 
aud these oils may, in many instances, be sepa- 
rated by the process of distillation ; but there 
are some of so fleeting and subtile a nature, 
that the heat necessary for conducting the pro- 
cess of distillation entirely destroys them ; for 
instance, no distillation, however carefully con- 
ducted, has hitherto accomplished the separa- 
tion of the oil-of-jasmine, which is extracted 
in a very different manner; jasmine flowers are 
moistened with almond oil, and then exposed 
to great pressure, which squeezes out the oil- 
of-jasmine mixed with oil-of-almonds. The 
greater number of oils, both fixed and volatile, 
are compounds of carbon, hydrogen, and oxygen, 
but a few are composed of carbon and hydro- 
gen alone ; as examples of these, I may men- 
tion oil-of-lemons and oil-of-turpentine, both of 
which, so far as relates to chemical composi- 
tion and properties, are precisely similar. The 
liquid sold under the name of scouring-drops, 
is merely distilled oil-of-lemons, and is much 
employed for the purpose of removing stains 
of grease from silk and linen. The substance 
named camphor, is a solid volatile oil, which is 
obtained very plentifully from various parts of 
the Lauras camphora, a native of Japan. 



288 RESIN — WAX. 

Volatile or essential oils are capable of being 
dissolved to a very limited extent by water, to 
which liquid they impart their peculiar tastes 
and smells. Rose, cinnamon, lavender, and 
peppermint-water are all of this nature. 

Very nearly allied in composition and pro- 
perties to fixed oils are substances of a resinous 
or bituminous nature. Common resin is ob- 
tained from various species of fir, where it 
exists in combination with oil-of-turpentine, 
and remains after the latter has been separated 
by the process of distillation. During the se- 
paration of turpentine from resin, a portion 
of the latter is decomposed into a black, viscid, 
substance, called tar ; and pitch is merely tar 
from which the volatile particles have been 
driven off by long boiling. 

Respecting the kingdom of organic nature 
to which the substance wax should be re- 
ferred, there has been a dispute ; some persons 
regarding it as a vegetable, and others as an 
animal principle. It is now, however, generally 
allowed, that although wax does occur as a na- 
tural vegetable production,yet this vegetable sub- 
stance differs from bees' -wax, the nature of which 
is considerably modified by the digestive organs 
of the bee ; indeed, the fact has been demon- 



CAOUTCHOUC, OR INDIA-RUBBER. 289 

strated, that bees fed on sugar alone will never- 
theless produce wax. 

The curious substance termed caoutchouc, or 
India-rubber, cannot be said to resemble any 
other body which chemistry makes known ; but 
in the nature of its components it approaches 
the resins. India-rubber is chiefly obtained from 
the Hterea, caoutchouc, and Jatroplia elastica, 
natives of South America, and of the Ficus 
Indica and Artocarpus integrifolia, which grow 
in the East Indies ; but many other vegetables 
yield it in smaller proportions. It exists both 
in the mulberry and lettuce, and, indeed, in every 
vegetableon which the silk-worm thrives ; hence 
it has been imagined that the tenacity of silk 
may, in some measure, depend on the presence 
of India-rubber. 

Under the head of bituminous substances 
are includednaphtha, petroleum, asphaltum, and 
the different varieties of pit-coal, besides some 
others. Naphtha is a colourless liquid, possess- 
ing a very strong odour, and occurring as a 
natural product in many parts of the world, 
more particularly Italy, the Grecian isles, the 
banks of the Caspian, and Persia. In the lat- 
ter country it supports the perpetual flames of 
the Persees, a set of enthusiasts who adore fire 

u 



290 FORMATION OF COAL. 

as a deity, and on this account are termed fire- 
worshippers. Naphtha is composed wholly of 
carbon and hydrogen ; hence, amongst other 
uses, it is employed to preserve the metals so- 
dium and potassium.* 

Pit-coal is the remnant of vast forests, which 
were overwhelmed by some grand convulsion of 
nature, and covered by strata of different kinds. 
Since which period they have been undergoing a 
gradual decomposition, subject in the meantime 
to an immense pressure from the superincumbent 
mass. Some specimens of coal are so perfect 
that the forms of the original vegetable fibres, 
and also of the leaves, are not yet destroyed ; 
so that even now, after the lapse of many ages, 
it is still possible to ascertain that the greater 
quantity of coal has been formed from gigantic 
ferns. 

Infinitely superior as beings of the animal 
world appear to all other forms and things in 
creation, their excellence is not the result of 
properties implanted in the primary elements 
which enter into their formation, but depends 
upon the principle of life implanted in them 
by the Deity. Vegetables are chiefly com- 

• Seep. 223. 



COMPOSITION OF BONES. 291 

posed of hydrogen, oxygen, and carbon, united 
in various quantities, in order to form a limited 
number of proximate principles. Animal tis- 
sues, in addition to the three bodies just men- 
tioned, contain a large proportion of nitrogen ; 
but other substances enter into their composi- 
tion in small quantities. The parts of the 
body of an animal may be divided into solids 
and fluids ; the latter being, for the most part, 
water, which composes nearly five-sixths by 
weight of the human body. 

Of the proximate principles which enter into 
the formation of animals, some are also found 
in the mineral world, whilst others are neces- 
sarily connected with animal organization. 

The bones are composed of a peculiar sub- 
stance termed by chemists, gelatine, holding 
together little particles of phosphate and car- 
bonate of lime : gelatine, when moist, is quite 
elastic ; but masses of the carbonate and 
phosphate of lime are brittle ; consequently, 
it is to the union of these three substances that 
we must attribute the admirable strength of 
bone ; which is not so brittle as to be readily 
broken,, and yet hard enough to support the 
weight and to withstand the violent action of 
the body without bending or losing its form. 



292 COMPOSITION OF BONES. 

I cannot pass over the description of bone 
without noticing an all-wise and admirable 
provision of nature against the different neces- 
sities of infancy and age. In children, the 
bones contain their greatest relative quantity 
of gelatine ; hence they are not hard and 
brittle but tough and elastic, by which means 
children are protected against many of the 
evil consequences that would otherwise arise 
from the falls and blows to which their 
sportive gambols continually expose them : 
gelatine, moreover, is susceptible of that de- 
velopement which it is necessary for every 
part of the body to undergo, and it is not until 
the period of growth ceases, and the hilarity of 
youth has yielded to the gravity of sober man- 
hood, that the deposition of carbonate and phos- 
phate of lime is complete. A few more fleeting 
years pass away, and then arrives the period of 
old age, when nature, gradually preparing for 
the approach of death, removes a portion of 
gelatine, and leaves the compounds of lime in 
excess. It is then that our poor frail bodies 
must avoid all blows and shocks ; we neces- 
sarily grow cautious and circumspect ; recol- 
lections of mortality crowd thickly upon the 
mind ; the consciousness that so much care is 



COMPOSITION OF BONES. 293 

necessary for our bodily safety admonishes us 
of our closing earthly career ; and proclaims, in 
language which cannot be misunderstood, that 
we have approached the confines of another 
world. 

As animals are not capable of generating the 
elements of which those compounds of lime 
are formed, it follows that they must be taken 
into the stomach with articles of food, chiefly 
solids : in the infant state, however, no solid 
food is taken, although there is an absolute 
necessity for a certain quantity of phosphate of 
lime to enter into the formation of infant bones: 
— the substance being naturally of an insoluble 
nature, one would not imagine that it existed 
in milk, but nature has accomplished her pur- 
pose by means of an acid, termed lactic, which 
is endowed with the property of rendering 
phosphate of lime soluble. 

Gelatine exists in many other parts of ani- 
mals besides bones. It is found abundantly in 
skin, tendons, hoofs, andhoms : glue, isinglass, 
size, and jelly are examples of this animal 
proximate principle, gelatine. The properties 
of gelatine are to dissolve when soaked or 
boiled with water, forming a jelly, and to yield 
precipitates with the tannic and gallic acids, 



294 FORMATION OF LEATHER. 

named tannate and gallate of gelatine ; on this lat- 
ter property depends the manufacture of leather, 
which substance is, chemically speaking, atanno- 
gallate of gelatine. Leather isformed by immers- 
ing skins, previously deprived of their hair and oil 
by lime, in a strong infusion of oak-bark, which 
contain the two acids in question ; tanno-gallate 
of gelatine, or leather, is the result. Lately 
the process of tanning has been conducted with- 
out oak -bark, the substance catechu being used 
in its stead. 

Gelatine is a very nutritive principle, and 
forms the basis of some of our most valuable 
articles of food. It is seldom procured from 
bones, because water at the ordinary boiling 
temperature, that is to say at two hundred and 
twelve degrees, is incapable of removing it from 
the accompanying salts of lime ; but if the 
boiling point be increased by an increase of 
pressure, then we may obtain gelatine from 
bones as well as from other more common 
sources. There is an instrument much used 
for the purpose, called Papin's, digester; its 
agency depending upon an elevation of the 
boiling point of water far above the usual de- 
gree. It is merely a very thick metallic vessel, 
supplied with a safety valve, which is pressed 



ANTEDILUVIAN SOUP. 295 

down with a degree of force proportionate 
with the elevation of the boiling point required. 
There is another method of obtaining gelatine 
from bones : the compounds of lime may be 
dissolved away by weak hydrochloric acid, 
leaving the gelatine isolated and capable of 
forming a solution with water by ordinary means. 
Gelatine as it exists in bone possesses a 
remarkable power of resisting decay ; conse- 
quently if at any time a civilized nation should 
be threatened with famine, it is probable that its 
inhabitants would set about the extraction of 
gelatine from bones, where it is stored up in 
security, but capable of being obtained in any 
case of emergency. Whilst on this topic I will 
mention an anecdote, but for its truth I cannot 
vouch. It is affirmed that some French philo- 
sophers, having found a bone of some creature 
which existed before the deluge, came to the 
extraordinary determination of regaling them- 
selves on antediluvian soup, which singular 
project was carried into effect by extracting the 
gelatine in the way I have already mentioned. 
Albumen is a proximate principle which is 
found in very many animal fluids and solids, 
but more particularly in the blood and in the 
white of eggs, particularly the latter. Albu- 



296 ALBUMEN FIBRIN. 

men may be resolved, like gelatine, into car- 
bon, hydrogen, oxygen, and nitrogen, and may 
be known from all other substances by the 
peculiar effects of heat, which converts it into 
a solid, as is well exemplified by the boiling of 
an egg. Albumen has the property of being 
precipitated by various re-agents, particularly 
the bichloride of mercury and salts of copper. 
On this peculiarity depends its efficacy as an 
antidote to those substances when they may 
have been taken as poisons. 

Fibrin is an animal principle, which is chiefly 
found in the muscles or flesh of animals and in 
the blood. It may be procured by various 
methods, but most easily by washing clots of 
blood until all the colouring matter is removed. 

The animal acids are very numerous, but 
none of them are of sufficient importance to 
merit a particular description on such an oc- 
casion as this. Among the principal I may 
name the lithic or uric, purpuric, rosacic, and 
formic acids. 

Animal bodies contain great quantities of 
oils and fats, possessing various degrees of 
hardness and liquidity. Many of these are 
employed as articles of food, and others are 
extensively used in the arts. The various kinds 



COMPOSITION OF soArs. 297 

of soap are combinations of alkalies with dif- 
ferent acids procured from oils and fats. Soaps 
may be formed either with animal or vegetable 
oils. In England, animal oils and fats are 
cheaper than those from the vegetable king- 
dom ; hence we use them in preparing soap ; 
but in Spain, where there is such an abundance 
of olive-oil, this is used for soap-making. Ani- 
mal oils are chiefly composed of two proximate 
principles, oleine and stearine ; the greater 
number of vegetable oils, of oleine and marga- 
rine, all of which, by the action of potash or 
soda, may be converted into oleic, stearic, and 
margaric acids ; which are no sooner formed 
than they unite with the alkalies, constituting 
oleate, margarafe, and stearate of potash or 
soda, all different varieties of soap. Soap made 
from tallow and soda is an oleo-stearate of that 
alkali, and chemically speaking, is a salt. 

Organic bodies are subject to a variety of 
intestine changes, commonly known by the 
name of fermentations ; these are usually di- 
vided into the saccharine, vinous, acetous, and 
putrefactive. That starch can be converted 
into sugar I have already mentioned, and on 
this depends the art of malting. Barley, in 
common with other grain, contains a large 



298 DIVISION OF VEGETABLES. 

quantity of starch, which is laid up as in a 
magazine for the young plants future nourish- 
ment. The operation of malting causes the 
grain to germinate, during which process starch 
becomes converted into sugar. 

But malting is only one instance of germi- 
nation ; a branch of vegetable physiology so 
important that it demands a more extended 
share of our attention. The term germination 
very prettily expresses its own meaning: the 
first bursting forth of a dormant embryo from 
the seed. Vegetables may be divided into 
those which bear flowers and those which do 
not. Only the former possess seeds, and hence 
they alone can be susceptible of germination, 
properly so called. The seeds of flowering 
plants are either possessed of one lobe or two, 
a fact of so much importance in botany, that 
upon its consideration is founded a divison of 
flowering plants into two great classes ; — mono- 
cotyledons, or those whose seeds have but one 
lobe ; and dicotyledons, or those the seeds of 
which have two or more. 

Germination proceeds somewhat differently 
in monocotyledonous from what it does in dico- 
tyledonous seeds, at least, so far as the mechan- 
ism of the operation is concerned ; but the 



THEORY OF GERMINATION. 299 

chemical changes are similar in either instance. 
The skin, or covering of a seed, is composed of 
at least three membranes, which, taken collec- 
tively, are called the testa ; this testa incloses 
the seed, properly so called, which is made up 
of a substance called albumen, and the embryo ; 
or, in some cases, of the embryo alone ; which 
latter is furthermore divided into radicle, plumule, 
and cotyledon, or cotyledons, as the case may be. 
If we biuy a dicotyledonous, or two-lobed seed, 
a few inches under the earth's surface, and all 
circumstances be favourable, the following 
changes ensue. By the absorption of moisture 
it swells and the two lobes separate, the radicle 
descends, the plumule ascends, and with it the 
two cotyledons, which are to be considered as 
rudimentary leaves : during the whole of this 
period there has been going on a chemical 
operation ; — oxygen has been absorbed from the 
atmosphere to combine with carbon of the 
starch, and form carbonic acid, which has es- 
caped, leaving sugar behind : in other words, 
sugar only differs from starch (as far as regards 
composition) in containing less carbon. Starch 
is not very soluble, and hence could not have 
been conveniently appropriated by the young 
plant to its own uses ; sugar, however, is sola- 



300 PROCESS OF MALTING. 

ble, and is in every respect well calculated to 
answer the purpose of nourishing the growing 
plant. Very low temperatures are unfavourable 
to germination, and hence it will not take place 
in the winter ; high temperatures are also un- 
favourable to the process, by destroying the 
vitality of the seed. Both these statements are 
exemplified in the operation of malting. The 
grain is made to pass through four distinct 
stages, called steeping, couching, flooring, and 
kiln-drying ; the object of which being, first, to 
set up artificial germination, and thus convert 
starch into sugar ; then, to destroy all vitality 
of the germ before it has had time to appro- 
priate to its own uses the sugar generated. 
The grain is first steeped in water for about 
two days, when it absorbs moisture, softens 
and swells considerably ; after which it is re- 
moved to the couch-frame, where it is laid up 
in heaps of thirty inches in depth for from 
twenty-six to thirty hours. In this situation 
the grain becomes warm, and acquires a dispo- 
sition to germinate ; but as the temperature in 
such large heaps would rise very unequally, 
and germination consequently be rapid in some 
portions and slow in others ; the process of 
flooring is employed. This consists in placing 



PROCESS OF MALTING. 301 

the grain in layers, a few inches thick, on large, 
airy, but shaded floors, where it remains for 
about twelve or fourteen days ; in short, until 
it is ascertained that the conversion of starch 
into sugar has been completed. During all 
this time it is frequently turned to prevent a 
matting together of the young germs ; and now 
the peiiod arrives when the maltster wishes to 
destroy that vital principle which has been 
brought into action through his agency. The 
young germ, hastening to leave its narrow cell, 
and to sprout forth into the world, has been 
busily preparing food for its infant growth, 
until its fully developed root should be able to 
gather nourishment from the earth : but its busy 
preparations receive a sudden check. The 
sprouting seeds are removed to a kiln ; where a 
high degree of temperature soon destroys the 
vital principle, and the elaborated sugar, in- 
tended as food for the young plant, is appropri- 
ated to the uses of rapacious man. 

It is well known that intoxicating drinks re- 
sult from the fermentation of different mixtures 
containing sugar : thus grape-juice contains a 
large proportion of sugar, and when fermented 
becomes converted into wine. Now the in- 
toxicating quality of wines, beer, cider, and in- 



302 ALCOHOL HOW PROCURED. 

deed all strong drinks, depends upon the pre- 
scence of alcohol, also called spirits-of-wine. 
Alcohol is very volatile, and therefore may be 
procured from various liquors by the process of 
distillation : rum, brandy, gin, and hollands all 
consist essentially of the same substance, alcohol, 
differently flavoured with various impurities. 

It was once doubted whether alcohol actu- 
ally existed in wine, or whether it was formed 
by the application of heat during distillation ; 
the doubt, however, no longer exists ; for al- 
cohol may be procured without distillation at 
all, although this process is usually resorted to 
for the sake of convenience. Fermented 
liquors consist of water, alcohol, and colouring 
matter : the latter may be removed by various 
means, and then there is a very easy method of 
separating alcohol and water, without the aid 
of distillation. Here is a little port-wine, to 
which I add some solution of di-acetate of lead,* 
and immediately there falls a very copious pre- 
cipitate of colouring matter, leaving the alcohol 
and water floating above. I now separate the 
colourless fluid from the colouring matter, by 
means of a filter or strainer of blotting-paper; 
and this being done I add to it some dry and 
* Commonly called Goulard's extract. 



STRENGTH OF WINE ASCERTAINED. 303 

hot carbonate of potash, commonly called salts- 
of-tartar, and very soon we shall observe that 
the fluid will be divided into two layers, one 
above the other ; the upper layer consists of 
pure alcohol, and the under layer of water, in 
which is dissolved carbonate of potash. 

The experiment that you have just witnessed 
may very often be turned to good account for es- 
timating the strength of wines. Instead of car- 
bonate of potash I might have used a substance 
termed chloride of calcium, which indeed is 
still more effective. There is no body so gene- 
rally available for removing water, as chloride 
of calcium, and with this intention it is very 
extensively employed in chemistry. 

In ascertaining the strength of wine, a pre- 
liminary operation was necessary to separate 
the colouring matter, but if I had wished to 
ascertain the strength of brandy, rum, or gin, all 
of which contain but very slight traces of colour- 
ing matter, then I might have applied the car- 
bonate of potash or chloride of calcium at once. 
It is satisfactorily proved, then, that alcohol is 
not formed during the process of distillation, 
but already exists in fermented liquors as a re- 
sult of the vinous fermentation. Alcohol is 
also generated during the preparation of bread, 



304 SPIRIT FROM BREAD. 

and if the oven be supplied with a proper ap- 
paratus, this alcohol may be collected. Some 
persons speak of the panary fermentation, pa/nis 
meaning bread, but it is at most but a modifi- 
cation of the vinous. It has been attempted to 
separate this alcohol from bread, and collect it 
for commercial purposes ; indeed, the project 
has been tried on a very large scale, and, to a 
certain extent, with success ;— that is to say, 
alcohol could be collected easily enough, but 
in order to do this it was found necessary to 
bake the bread so dry that no one could eat it : 
hence, the scheme was abandoned, and much 
(I should imagine) to the satisfaction of every 
rightly thinking member of the community ; for 
no one who reflects on the ease with which 
alcohol is obtained from other sources, and who 
witnesses the hurried strides with which the 
victim of a desire for spirituous liquors hastens 
towards his early grave, would feel pleasure in 
knowing that bread, the staff of life, — the stand- 
ard food of man, was obliged, by a set of greedy 
speculators, to yield a fluid which, when abused, 
has been, and still continues to be, the greatest 
bane of society. 

Very nearly allied to alcohol is the class of sub- 
stances termed ethers. Fewwords have had the 



MEANING OK THE TERM ETHER. 305 

misfortune to bo applied in such a loose and inde- 
finite sense as the word ether. The poets use the 
term ether for the atmosphere, or something far 
beyond the atmosphere, and even beyond the 
universe itself. Natural philosophers some- 
times make use of the same expression to indi- 
cate an imaginary fluid, which, when agitated 
and impelled into waves or undulations gives 
rise to the sensation of light ; and, lastly, the 
same term, ether, is applied to certain volatile 
fluids, which are formed by the action of various 
acids on alcohol ; — in which sense I now intend 
using it myself. If sulphuric acid be distilled 
with alcohol, we obtain as a result sulphuric 
ether; if nitric acid, nitric ether; if hydrochloric 
acid, hydrochloric ether : in short, there are but 
very few strong acids which are not capable of 
forming ethers with alcohol, and the process is 
termed etherification. The composition of ethers 
produced by different acids varies a good deal, 
and consequently the theory of etherification 
must be different in every case. There are 
many ways of regarding the mode in which the 
elements which constitute ethers are united to- 
gether ; but it is in general imagined that they 
are modifications of an imaginary base, which 
has been termed etherine. Etherine consists of 
carbon and hydrogen, in the following ratio : — 

x 



-306 THEORY OF ETHKRIFICATION. 

( 4 Carbon. 
Etherine -J 

(. 4 Hydrogen. 

It would neither be very instructive nor very 
easy to go through the process of making the 
different ethers : none of them are of much im- 
portance, with the exception of sulphuric ether, 
but the latter demands a little attention. On 
distilling a mixture of alcohol and sulphuric 
acid in a glass retort, by the heat of a spirit- 
lamp, and adapting a cooled receiver, sulphuric 
ether comes over. It is a liquid possessing a very 
peculiar odour ; having a great tendency to fly 
off in vapour, and not very miscible with water. 
The theory of the production of sulphuric ether 
has been variously stated. The account which 
was formerly given of the process is the follow- 
ing : that alcohol was composed of one equiva- 
lent of the substance etherine and two of water; 
and sulphuric ether, of one of etherine and one 
of water ; that sulphuric acid abstracted one of 
water, and ether passed over. This theory has 
been a little modified, but even at the present 
time it is essentially true, the result being as I 
have mentioned ; but in the space elapsing be- 
tween the first addition of sulphuric acid and 
the evolution of the ether, there is generated an 
intermediate substance, termed sulpho-vinic 



PUTREFACTIVE FERMENTATIONS. 307 

acid, which, however, is no sooner formed than 
the heat necessary for the experiment destroys 
its evanescent existence ; therefore we need not 
take much account of it in explaining the form- 
ation of sulphuric ether. 

The acetous fermentation is that which gives 
rise to the formation of vinegar or acetic acid, and 
the putrefactive fermentation is only another term 
for decay, consisting in the change of organic 
principles, into the more simple forms of inor- 
ganic existence. 

As the. complicated structure of an animal or 
a plant owes its formation to the mysterious 
agency of life, so it is only by the same life that 
its preservation is maintained. When deprived 
of this, the inorganic forces exercising their full 
sway, agaiu resolve it into simple forms : — it 
withers and decays. This change, then, is no 
less certain than death itself ; sooner or later it 
awaits us all, and every living thing. 

The giants of the vegetable world; the stately 
cedar, and the sturdy oak ; the pine, — which 
braves the rigours of the Alpine snow ; and the 
towering palms, — which greet a burning sun, 
await their doom, no less than the lowly daisy 
or the spreading moss : — they all must die ! The 
majestic elephant, — which shakes the earth on 
which he treads; the mighty whale, — revelling 



308 PUTREFACTIVE FERMENTATION. 

to-day in all the plenitude of power — the lion, the 
tiger, — themselves the harbingers of death, yield 
alike to the fate of the sparrow or the worm. 
Even the beauty of the human form, impressed 
as it is with the image of God, — and shining in 
grand pre-eminence, beyond the creatures of 
mere earthly mould, — beamingwith all the graces 
of youth, or standing erect in manhood's dig- 
nity ; — this too must die ! In fine, it is decreed 
that death shall be the fate of every living 
thing, — and after death decay: thattheprinciple 
of life, once implanted, shall cease to maintain 
its sway ; that the little atoms, which, under its 
guidance, budded forth into leaves and flowers, 
or shone in the statelier majesty of animated 
forms, shall resolve themselves again into sim- 
plerstates; — and, no longer directed by theprin- 
ciple of life, shall roam like little wanderers on 
creation's broad expanse. 

In contemplating the process of decay orputre- 
faction, the mere common observer experiences 
no sensations but those of disgust ; with the che- 
mist it is far otherwise ; he does not regard death 
as a calamity — neither do ideas of destruction 
ever enter his mind. He sees the elements of 
former beings springing up into new states of 
existence, and teeming with all the freshness 
of infant life : he recognizes in all those changes 



THE LECTURER'S FAREWELL. 309 

the workings of a heavenly hand ; and remem- 
bers, with fond satisfaction, that the Being who 
condescends to dissolve and re-arrange the ele- 
ments of a lowly plant or creeping worm, will 
never cease to minister to the proper wants, or 
neglect the guidance of that most noble of all 
earthly beings, — into which he himself has 
breathed the breath of life, and implanted a 
conscious and never-dying soul. 

When surveying the vast field of organic 
chemistry, the mind loses itself in the multi- 
plicity of combinations which we see taking 
place around us. Myriads of little atoms 
ever combining, separating, and recombin- 
ing, seem to treat the inquisitive philosopher 
with playful disdain, and to defy his curi- 
osity. We have hitherto followed them at an 
easy pace, without much fatigue and with some 
little amusement ; but now they run wild in 
their gambols, and to keep pace with them might 
cause us some fatigue : — I bid them all fare- 
well ! and you, — my young friends, — I also bid 
farewell ; — for my Lectures on Chemistry are 
finished. We entered upon the study of our 
science with sportiveness and mirth ; but to- 
wards the conclusion of our labours we have 
been compelled to become more serious, and to 



310 CONCLUSION. 

use language more in accordance with the na- 
ture of our subject. As a young lion torn 
from the forest is tame and playful, allowing 
caresses, and joining in every frolic, so we 
found chemistry ; but as it grew up to its full 
size and formidable strength, — it became a 
thing no longer to be played with ; — demanding 
all care, attention, and respect. If I have 
grown dull in the prosecution of my task ; if I 
have used language too difficult or too unpleas- 
ing ; in short, if you have been less interested 
by the termination than by the commencement 
of my Lectures, do not judge me too harshly, I 
beseech you, but attribute some of these defects 
to the increasing difficulties of my subject. 

And now accept my best wishes for the pros- 
perity of our little institution : if my labours 
should be deemed of any service in promoting 
its advancement I certainly will come again, 
and lecture on some other subject. Once more 
1 bid you farewell. 

THE END. 



J. Uickerby, Printer, Sherbount Lane. 



MR. SCOFFERN, 

CONTINUES TO HOLD 

Private JEeMial €U$m 

AT 

No. 18, BARBICAN. 



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(Latin,) and the collateral Medical Sciences. Gen- 
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tunity of studying Materia Medica by the assistance 
of specimens procured at the warehouses of Apothe- 
caries' Hall, and of attending a course of Practical 
Chemistry, for which certificates, recognized at the 
Hall, will be given. 

TERMS. 

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any day except Saturday and Sunday ; or, at Mr. 
Scoffern's residence, No. 26, King Square, Goswell 
Road. 



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